Ui upgrade

# New UI #
- setup ```Sass```
- quick UI design and update
  - most changes are on the main/login page
  - no specific changes on the main/chat page yet besides that it inherits the background and ```<nav>``` style changes

### NOTE: ###
there are some ```.jade``` files in this pull request that have just indentation changes. As I am not sure if we have set an indentation rule (e.g. how many spaces to use?) so I just used the standard 1 tab = 2 spaces rule. Just FYI because jade often complains when tabs and spaces are used simultaneously in a file.

### Main ###
![image](https://cloud.githubusercontent.com/assets/2268040/3062004/b3d09eac-e213-11e3-9016-1316d8439e1f.png)

### Chat ###
![image](https://cloud.githubusercontent.com/assets/2268040/3061987/3c84f2f8-e213-11e3-8537-fbf3230a02b4.png)