update spec with header and headerbyhash rpc methods (#374)

spec/rpc/README.md

@@ -24,6 +24,8 @@ This file defines the JSON-RPC spec of Tendermint. This is meant to be implement
   | [Status](#status)                       |                             ✅                              |                                 ✅                                 |
   | [NetInfo](#netinfo)                     |                             ✅                              |                                 ✅                                 |
   | [Blockchain](#blockchain)               |                             ✅                              |                                 ✅                                 |
+  | [Header](#header)                       |                             ✅                              |                                 ❌                                  |
+  | [HeaderByHash](#headerbyhash)           |                             ✅                              |                                 ❌                                 |
   | [Block](#block)                         |                             ✅                              |                                 ✅                                 |
   | [BlockByHash](#blockbyhash)             |                             ✅                              |                                 ❌                                 |
   | [BlockResults](#blockresults)           |                             ✅                              |                                 ✅                                 |
@@ -49,7 +51,6 @@ Timestamps in the RPC layer of Tendermint follows RFC3339Nano.  The RFC3339Nano
 This means if a block has a timestamp like: `1985-04-12T23:20:50.5200000Z`, the value returned in the RPC will be `1985-04-12T23:20:50.52Z`.
 
 
-
 ## Info Routes
 
 ### Health
@@ -272,13 +273,130 @@ curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\
 }
 ```
 
+### Header
+
+Get a header at a specified height.
+
+#### Parameters
+
+- `height (integer)`: height of the requested header. If no height is specified the latest height will be used.
+
+#### Request
+
+##### HTTP
+
+```sh
+curl http://127.0.0.1:26657/header
+
+curl http://127.0.0.1:26657/header?height=1
+```
+
+##### JSONRPC
+
+```sh
+curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"header\",\"params\":{\"height\":\"1\"}}"
+```
+
+#### Response
+
+```json
+{
+  "id": 0,
+  "jsonrpc": "2.0",
+  "result": {
+    "header": {
+      "version": {
+        "block": "10",
+        "app": "0"
+      },
+      "chain_id": "cosmoshub-2",
+      "height": "12",
+      "time": "2019-04-22T17:01:51.701356223Z",
+      "last_block_id": {
+        "hash": "112BC173FD838FB68EB43476816CD7B4C6661B6884A9E357B417EE957E1CF8F7",
+        "parts": {
+          "total": 1,
+          "hash": "38D4B26B5B725C4F13571EFE022C030390E4C33C8CF6F88EDD142EA769642DBD"
+        }
+      },
+      "last_commit_hash": "21B9BC845AD2CB2C4193CDD17BFC506F1EBE5A7402E84AD96E64171287A34812",
+      "data_hash": "970886F99E77ED0D60DA8FCE0447C2676E59F2F77302B0C4AA10E1D02F18EF73",
+      "validators_hash": "D658BFD100CA8025CFD3BECFE86194322731D387286FBD26E059115FD5F2BCA0",
+      "next_validators_hash": "D658BFD100CA8025CFD3BECFE86194322731D387286FBD26E059115FD5F2BCA0",
+      "consensus_hash": "0F2908883A105C793B74495EB7D6DF2EEA479ED7FC9349206A65CB0F9987A0B8",
+      "app_hash": "223BF64D4A01074DC523A80E76B9BBC786C791FB0A1893AC5B14866356FCFD6C",
+      "last_results_hash": "",
+      "evidence_hash": "",
+      "proposer_address": "D540AB022088612AC74B287D076DBFBC4A377A2E"
+    }
+  }
+}
+```
+
+### HeaderByHash
+
+#### Parameters
+
+- `hash (string)`: Hash of the header to query for.
+
+#### Request
+
+##### HTTP
+
+```sh
+curl http://127.0.0.1:26657/header_by_hash?hash=0xD70952032620CC4E2737EB8AC379806359D8E0B17B0488F627997A0B043ABDED
+```
+
+##### JSONRPC
+
+```sh
+curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"header_by_hash\",\"params\":{\"hash\":\"0xD70952032620CC4E2737EB8AC379806359D8E0B17B0488F627997A0B043ABDED\"}}"
+```
+
+#### Response
+
+```json
+{
+  "id": 0,
+  "jsonrpc": "2.0",
+  "result": {
+      "header": {
+        "version": {
+          "block": "10",
+          "app": "0"
+        },
+        "chain_id": "cosmoshub-2",
+        "height": "12",
+        "time": "2019-04-22T17:01:51.701356223Z",
+        "last_block_id": {
+          "hash": "112BC173FD838FB68EB43476816CD7B4C6661B6884A9E357B417EE957E1CF8F7",
+          "parts": {
+            "total": 1,
+            "hash": "38D4B26B5B725C4F13571EFE022C030390E4C33C8CF6F88EDD142EA769642DBD"
+          }
+        },
+        "last_commit_hash": "21B9BC845AD2CB2C4193CDD17BFC506F1EBE5A7402E84AD96E64171287A34812",
+        "data_hash": "970886F99E77ED0D60DA8FCE0447C2676E59F2F77302B0C4AA10E1D02F18EF73",
+        "validators_hash": "D658BFD100CA8025CFD3BECFE86194322731D387286FBD26E059115FD5F2BCA0",
+        "next_validators_hash": "D658BFD100CA8025CFD3BECFE86194322731D387286FBD26E059115FD5F2BCA0",
+        "consensus_hash": "0F2908883A105C793B74495EB7D6DF2EEA479ED7FC9349206A65CB0F9987A0B8",
+        "app_hash": "223BF64D4A01074DC523A80E76B9BBC786C791FB0A1893AC5B14866356FCFD6C",
+        "last_results_hash": "",
+        "evidence_hash": "",
+        "proposer_address": "D540AB022088612AC74B287D076DBFBC4A377A2E"
+      }
+    }
+  }
+}
+```
+
 ### Block
 
 Get block at a specified height.
 
 #### Parameters
 
-- `height (integer)`: height of the requested block. If no height is specified the latest block will be used.
+- `height (integer)`: height of the requested block. If no height is specified the latest height will be used.
 
 #### Request