First draft for gophercloud intro blog post

* URLs will likely change, those are placeholders (at least the one for docs)
Personal tic: I'm not fond of claiming that things are straightforward; let readers decide that for themselves. Also, an experienced Go programmer is likely to already have their GOPATH set. How about:

> To install Gophercloud, make sure that you have [your `$GOPATH` set properly](https://golang.org/doc/code.html#GOPATH), then use the following command:
> ```bash
> go get github.com/rackspace/gophercloud
> ```