Notifications feature

Notifications have been added as discussed in #141. Currently, the only information that we can notify people about is comments. As we build follow/forking features - I'll add them to this.

[Here's](http://glittergallery-ropaku.rhcloud.com/notifications) a working copy. To test this, you'll have to create two accounts and try commenting on each other's projects. If you don't want to go through the pain of doing that, just post the URL of your public project below, and I'll comment on it :) 

For now, you'll have to visit `/notifications` to see the notifications page as there is no visible link to it. 

Here are some screenshots : 

![screenshot from 2014-07-03 00 42 22](https://cloud.githubusercontent.com/assets/3893573/3460978/3ee1bb6a-021d-11e4-9fff-34383c807052.png)
![screenshot from 2014-07-03 00 42 57](https://cloud.githubusercontent.com/assets/3893573/3460980/412d2bfc-021d-11e4-9f20-fe545032be5f.png)