Update to scoverage version 1.0

Test coverage in core and play improved to maximum available.
Update to Travis build definition - coverage

Contrubution guidlines updated for new coverage setup.
Merge pull request #46 from VirtusLab/feature/scoverage

Feature/scoverage
Initial version for Slick 3.0-M1

`unicorn-core` compiles, all tests pass.

`unicorn-play` compiles, tests fails due to no `plya-slick` for 3.0-M1.