- 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