Correction of typos

I noticed a typo in the recent [Building an Ember App with RailsAPI - Part 1 article](http://reefpoints.dockyard.com/ember/2013/01/07/building-an-ember-app-with-rails-api-part-1.html) and figured I might as well just give the rest of the posts a once-over.

Nothing too aggressive (branding capitalization, grammar, etc.), just typos where I spotted them.