Clarify --tests usage

After reading the existing --tests documentation it still wasn't clear to my co-worker or me that the flag would only match the names of the classes, but not the path or class name.  This should make it clear.
Adding basic infrastructure for unit testing.   This allows us to set up sbt projects with junit
and then test the coherency of such a project.   This level of automation is needed
for safe releasing on demand.

Review by @benmccann
Add travis CI integration so we can automate testing pull requests.
Add newlines
Merge pull request #44 from sbt/wip/integration-tests

Add some simple integration tests so we know we can release
Merge pull request #42 from ebuchanan/master

Clarify --tests usage