Added ability to select best answer for user's own questions

### Changes
* Added form to each answer that allows you to select it as the best answer. 
* Added best answer route, ```/bestanswer```
* Added AJAX to asynchronously update the best answer when selected by the user.
* Corrected minor view typos in ```answer```
* Fixed typo in ```user-spec``` and configurated RSpec to automatically ```--format documentation```

### Micro Challenge 1: AJAX
* Added AJAX to asynchronously update the best answer when selected by the user
* Ideas for stretch include: remove best answer button from answer already selected, auto-refresh page

### Micro Challenge 2: Virtual Attributes 
![virtual-attributes](https://f.cloud.github.com/assets/770277/934599/e284cd14-006d-11e3-8cb9-50e54d67d8af.png)
*form screenshot & micro-challenge information*