adding CI Provider for TeamCity 8.1.x

Hi Frederik,

I added a TeamCity CI provider. 

It is unit tested as well as manually tested against TeamCity 8.1.x. 

If you want to verify it you can download TeamCity for free. In order to use the TeamCity REST API without credentials you have to enable guest access. 

You should configure the widget with the TeamCity host (e.g. `http://localhost:8111` without trailing `/`) and the project id. If you hover a project in TeamCity you see a link like `http://localhost:8111/project.html?projectId=peeone&tab=projectOverview`. In that example `peeone` is the project name that needs to be configured when setting up the widget.

I although updated ruby to 2.1.0. I hope this is fine;) Further I added `gem sqlite3` in order to skip installing mysql. To clean things up I extended `.gitignore`.

Regards, Leif