Merge PR #1429: tools: Add ineffassign linter

* tools: Add ineffassign linter

This errors on assignments that don't actually do anything. i.e.

x, err := myFunc(1)
y, err = myFunc(2)

This will call out that the first function's call error was never
used.

* Fix makefile, add misspell to makefile

examples/democoin/cmd/democoind/main.go

@@ -34,6 +34,9 @@ func CoolAppGenState(cdc *wire.Codec, appGenTxs []json.RawMessage) (appState jso
         "trend": "ice-cold"
       }`)
 	appState, err = server.AppendJSON(cdc, appState, key, value)
+	if err != nil {
+		return
+	}
 	key = "pow"
 	value = json.RawMessage(`{
         "difficulty": 1,