- activate travis build

Hy,

to prepare the multidbcake example that i want to push (https://github.com/nafg/slick-migration-api/issues/1). I activate travis build and coveralls coverage report for the project.

On travis there also the mysql and postgres test are succesfully performed take me a while to get it work but here it is.
I start use your migration api in my https://github.com/pussinboots/unitcover project and it saves me a lot of time to think about how i can perform database migration for the heroku production version.

So thanks for the simple to use migration api
great work
What is the purpose of these tests, why do they even exist?