Redesign login page

Resigned responsive login page.

I am a little bit concerned regarding the survey related code.  The ```if mhub?``` and ```if @survey``` clauses make it difficult to refactor but also I'm not sure how to test this.  Seems like too much business logic in the view layer...  Would someone test if this works?

![login-mobile](https://f.cloud.github.com/assets/3383/2069248/1342624e-8d14-11e3-82de-7b6d13d54a9d.png)
![login-tablet](https://f.cloud.github.com/assets/3383/2069246/133d365c-8d14-11e3-8832-a3ef80ff3689.png)
![login-widescreen](https://f.cloud.github.com/assets/3383/2069247/133e1342-8d14-11e3-9de3-c319c566d576.png)