gor命令增加提示帮助，类似输入go的时候提示

[astaxie]

输入go的提示如下：

➜ ~ go Go is a tool for managing Go source code.

Usage:

go command [arguments]

The commands are:

build       compile packages and dependencies
clean       remove object files
doc         run godoc on package sources
env         print Go environment information
fix         run go tool fix on packages
fmt         run gofmt on package sources
get         download and install packages and dependencies
install     compile and install packages and dependencies
list        list packages
run         compile and run Go program
test        test packages
tool        run specified go tool
version     print Go version
vet         run go tool vet on packages

[wendal]

基本支持了