If there's only one blog show it in My Blogs

Instead of showing the lists of blogs by default with just one blog and
the "Add site" option, push that blog controller by default.

You can still go back and when you tap "My Blogs" again it'll pop

Related to #333 / #388. @mikejohnstn 

![my-blogs](https://f.cloud.github.com/assets/8739/1556454/bcbefec0-4ed2-11e3-8981-4954c8fcc82d.gif)