User auth

 @anthonye2007 please look over the changes and reply to the question in the "Not completed yet" section

Several changes: 

- Added devise for authentication
- Finished fixing ORM mapping (change to mongoid)
- Add user model, views, authentication and requirement to be logged in - "locked" everything down
- Several minor formatting/name changes
- Added ability to update user profile
- Added site logo - two sizes available.  We can always change the logo, color of the logo, etc.  I just created this so we have something.  Feel free to change this to meet "HCI requirements", color theory requirements, etc.


Not completed yet:
You may notice I included Omniauth gems.  I plan to add support (in the very near future - hopefully this weekend) for logging in with some social media platform. Originally, I was going to support multiple (see gemfile changes below), but I think I will just stick with one.  The reason - we have to register our app through each SM platform's website to gain access.  I'd rather not waste too much time on a non-essential feature.  We can always go back and add more later, if we want.  I will check out Facebook first (most popular?), but I think it was a pain the last time I dealt with them.  If Facebook fails, I think Twitter was pretty straight forward (the app registration process).  Do you have preferences for which we support?