First draft for gophercloud intro blog post

* URLs will likely change, those are placeholders (at least the one for docs)
1. 'Strive' is a verb. s/constant strive/on-going effort
2. s/gophercloud is a/Gophercloud is a
3. s/Rackspace specific support/ Rackspace support
4. For the last sentence, maybe something like: "Rackspace and Openstack users can seamlessly integrate it into their existing applications, and users of other Openstack-based clouds can extend it to work with theirs."