add govendor tool.

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

Golint requires Go 1.6 or later.

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

install cloc into golang bin folder.

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

Drop support for Go 1.5.

golang/lint@a428635

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