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>

.travis.yml

@@ -10,13 +10,14 @@ git:
   depth: 3
 
 install:
-  - go get -v github.com/kardianos/govendor
-  - govendor sync
-  - go get -u github.com/campoy/embedmd
+  - make install
 
 script:
-  - embedmd -d README.md
-  - go test -v -covermode=count -coverprofile=coverage.out
+  - make vet
+  - make fmt-check
+  - make embedmd
+  - make misspell-check
+  - make test
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)