Added tests using scripted plugin

This pull request just sets up the scripted plug in and automates some simple tests. I upgraded the build version number to version of sbt-liquibase to "0.5.1" even though the generated artifacts would not be any different than the current "0.5.0" release so that testing would not be impacted by local or cached versions of the current release.

I'm hoping to send some additional pull requests in the coming weeks but wanted to establish a testing baseline. There were some issues with the scripted plugin changes but I was able to build successfully with setting an sbt versions of 0.11.3 and 0.12.2.