modules/coin/rest: implemented CreateRole

* Note: Role must be a hex string, as enforced in tests/rest/cli.sh

```shell
$ curl -X POST http://localhost:8998/build/create_role --data \
'{
  "role":"DEADBEEF", "seq": 1,
  "min_sigs": 1,
  "signers": [{
    "addr": "4FF759D47C81754D8F553DCCAC8651D0AF74C7F9", "app": "role"
  }]
}'
```

```HTTP
HTTP/1.1 200 OK
Content-Type: application/json
Date: Tue, 08 Aug 2017 19:15:13 GMT
Content-Length: 387

{
  "type": "chain/tx",
  "data": {
    "chain_id": "test_chain_id",
    "expires_at": 0,
    "tx": {
      "type": "role/create",
      "data": {
        "role": "DEADBEEF",
        "min_sigs": 1,
        "signers": [
          {
            "chain": "",
            "app": "role",
            "addr": "4FF759D47C81754D8F553DCCAC8651D0AF74C7F9"
          }
        ]
      }
    }
  }
}
```

Updates #200

cmd/baseserver/README.md

@@ -24,11 +24,17 @@ Route | Method | Completed | Description
 /sign|POST|✔️|Sign a transaction
 /tx|POST|✖️|Post a transaction to the blockchain
 /seeds/status|GET|✖️|Returns the information on the last seed
+/build/create_role|POST|✔️|Creates a role. Please note that the role MUST be valid hex for example instead of sending "role", send its hex encoded equivalent "726f6c65"
+
+## Preamble:
+In the examples below, we assume that URL is set to `http://localhost:8889`
+which can be set for example
+URL=http://localhost:8889
 
 ## Sample usage
 - Generate a key
 ```shell
-$ curl -X POST http://localhost8998/keys --data '{"algo": "ed25519", "name": "SampleX", "passphrase": "Say no more"}'
+$ curl -X POST $URL/keys --data '{"algo": "ed25519", "name": "SampleX", "passphrase": "Say no more"}'
 ```
 
 ```json
@@ -47,7 +53,7 @@ $ curl -X POST http://localhost8998/keys --data '{"algo": "ed25519", "name": "Sa
 
 - Sign a key
 ```shell
-$ curl -X POST http://localhost:8998/sign --data '{
+$ curl -X POST $URL/sign --data '{
     "name": "matt",
     "password": "Say no more",
     "tx": {
@@ -114,3 +120,41 @@ $ curl -X POST http://localhost:8998/sign --data '{
   }
 }
 ```
+
+- Create a role
+```shell
+$ curl -X POST $URL/build/create_role --data \
+'{
+  "role": "deadbeef",
+  "signers": [{
+    "addr": "4FF759D47C81754D8F553DCCAC8651D0AF74C7F9",
+    "app": "role"
+  }],
+  "min_sigs": 1,
+  "seq": 1
+}'
+```
+
+```json
+{
+  "type": "chain/tx",
+  "data": {
+    "chain_id": "test_chain_id",
+    "expires_at": 0,
+    "tx": {
+      "type": "role/create",
+      "data": {
+        "role": "DEADBEEF",
+        "min_sigs": 1,
+        "signers": [
+          {
+            "chain": "",
+            "app": "role",
+            "addr": "4FF759D47C81754D8F553DCCAC8651D0AF74C7F9"
+          }
+        ]
+      }
+    }
+  }
+}
+```

cmd/baseserver/main.go

@@ -13,6 +13,7 @@ import (
 	"github.com/tendermint/basecoin/client/commands"
 	rest "github.com/tendermint/basecoin/client/rest"
 	coinrest "github.com/tendermint/basecoin/modules/coin/rest"
+	rolerest "github.com/tendermint/basecoin/modules/roles/rest"
 	"github.com/tendermint/tmlibs/cli"
 )
 
@@ -50,6 +51,9 @@ func serve(cmd *cobra.Command, args []string) error {
 		// Coin query account handler
 		coinrest.RegisterQueryAccount,
 
+		// Roles createRole handler
+		rolerest.RegisterCreateRole,
+
 		// Basecoin sign transactions handler
 		rest.RegisterSignTx,
 		// Basecoin post transaction handler