Gutter improvements

Before:
![image](https://cloud.githubusercontent.com/assets/801452/5535285/604486ba-8a40-11e4-86e2-de96b81f85ab.png)

After:
![image](https://cloud.githubusercontent.com/assets/801452/5535289/7349b078-8a40-11e4-9f0b-17b4aeb61386.png)

* Corrected date format
* Set the last message and timestamp upon sending and receiving messages
* Made the conversation name and last message overflow into ellipsis