Add Makefile to check the following thing (#947)

* Add Makefile to check the following thing.

* vet check
* fmt check
* embedmd check
* misspell check

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* remove unused variable.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

context.go

@@ -87,7 +87,7 @@ func (c *Context) HandlerName() string {
 
 // Handler returns the main handler.
 func (c *Context) Handler() HandlerFunc {
-        return c.handlers.Last()
+	return c.handlers.Last()
 }
 
 /************************************/