Add complexity analysis to code-check; remove custom limit from coverage

Squashed commit of the following:

commit 4319a3ced081a6ce76d077f96cc9d2e868dca3ab
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 29 10:17:42 2014 +0100

    Adjust readme, remove low limit from coverage

commit 6d67f33787e4f379e6f89b44596ba7d8642ab01d
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 29 08:25:57 2014 +0100

    Enabled complexity analysis with flay