simplified clone: using go get

Documentation/getting-started.md

@@ -5,7 +5,7 @@
 Dex requires a Go installation and a GOPATH configured. For setting up a Go workspace, refer to the [official documentation][go-setup]. Clone it down the correct place, and simply type `make` to compile the dex binary.
 
 ```
-$ git clone https://github.com/coreos/dex.git $GOPATH/src/github.com/coreos/dex
+$ go get github.com/coreos/dex
 $ cd $GOPATH/src/github.com/coreos/dex
 $ make
 ```