Travis CI

This is proposition.

To turn this on owner of repo should:
- go to [travis-ci.org](https://travis-ci.org/)
- accounts (top right)
- scalatest/scalatest ON

=> next commit to PR will force travis build.
Due to plenty commits of changing docs, please keep in mind [this](http://docs.travis-ci.com/user/how-to-skip-a-build/)

I have to change a bit jvm options, to have successful compilation under travis, due to [java.lang.OutOfMemoryError: GC overhead limit exceeded](https://travis-ci.org/dmakhno/scalatest/jobs/18091266)

Unfortunately, I didn't have "green" build, because some of tests generally from org.scalatest.concurrent randomly fail:
- [org.scalatest.concurrent.AsyncAssertionsSpec](https://s3.amazonaws.com/archive.travis-ci.org/jobs/18115480/log.txt)
- [org.scalatest.RandomTestOrderSpec, org.scalatest.concurrent.AsyncAssertionsSpec, org.scalatest.tools.FrameworkSuite](https://s3.amazonaws.com/archive.travis-ci.org/jobs/18115481/log.txt)
- [org.scalatest.concurrent.TimeoutsSpec](https://s3.amazonaws.com/archive.travis-ci.org/jobs/18123782/log.txt)
- [org.scalatest.concurrent.TimeoutsSpec, org.scalatest.RandomTestOrderSpec, org.scalatest.tools.FrameworkSuite](https://s3.amazonaws.com/archive.travis-ci.org/jobs/18123783/log.txt)

P.S. I took jdk settings from [scalaz](https://github.com/scalaz/scalaz/blob/scalaz-seven/.travis.yml), they might be changed on demand.