Use regex to ignore files on server

In order to let files persist on the server that I don't want on my local machine
As a jekyll-user
I want to have an exclude filter for files to delete


### Before
![Before ignore_on_server](https://f.cloud.github.com/assets/50284/377472/a941f936-a4bb-11e2-9dd2-34cbc1be0a6b.png)

### After
![After ignore_on_server!](https://f.cloud.github.com/assets/50284/377473/b0eece52-a4bb-11e2-891b-87362d6fc975.png)