Show cookbook versions dropdown

:fork_and_knife: @bcobb After consulting with @danvolkens this pull request changes the way versions are viewed/switched between. I initially started looking into how we could reduce our use of spaghetti jQuery but then started to question the value of the original feature. This changes it up so the current version you're viewing of a cookbook is displayed in the cookbook header. You can then click on the version and a drop down of all of the previous versions are displayed so you can switch between them. Obviously the rest of the view is still being styled in @danvolkens UI branch but here's kind of sort of what it will look like. Not only does it help us get rid of a bunch of JS but I think it calls out the versions feature a lot better.

![screen shot 2014-03-27 at 2 23 44 pm](https://cloud.githubusercontent.com/assets/316507/2541473/708d6e2a-b5dd-11e3-81c8-57347fcf2c13.png)