Add option to filter dot files.

This lets you hide those annoying hidden files and directories like ***.ssh*** or ***.bashrc*** and you can still open them with ***Ctrl + P*** if you really need to.

![image](https://cloud.githubusercontent.com/assets/1369748/3485443/73e8ec7c-03dd-11e4-8d09-6b3ae3697bef.png)