Added styles to flash messages.

Currently, the flash messages are not stylised and hence, can be missed when some operation is performed.

![flash](https://f.cloud.github.com/assets/1005808/2229397/8cdacf60-9aed-11e3-8630-b3d20dbe902d.jpg)

Added a helper that adds BS classes to the flash messages for better rendering, making it more readable :)

![flash2](https://f.cloud.github.com/assets/1005808/2229409/edda7360-9aed-11e3-8c50-06bf47205bfd.jpg)