Rake tasks to simplify testing.

This issue is duplication of pull request for netzke-core [#51](https://github.com/netzke/netzke-core/pull/51). It allows run test with only ```rake test``` command. Also it allows to prepare test app with ```rake test:prepare``` command.

Current issues and questions:
* not all test passed, I'm not sure why.
* could we join core and basepack projects through some dev tools to escape duplication here?
* is it really necessary to use mysql2 db for test in basepack project ? think that sqlite is more suitable for testing as it is more portable.
* currently ```rake test``` can't be run without ```bundle exec``` prefix, not sure that it should work this way.