Links, hashtags and mentions are now formatted as links no matter their order.

This should resolve #22

![twister_hashtag_link](https://f.cloud.github.com/assets/5058257/1909965/d0809a2a-7d0a-11e3-9ac1-89dcc465ceb6.png)

Edit: Please let me know if I should rewrite the commit and any style issues I should consider.