Migration to Scala 2.11, scalatest 2.2 and Intellij IDEA 14

[nietaki]

When I cloned the repository I had problems opening it with current Intellij IDEA, so I made a couple of changes to keep the repository up to date

1. removed the reference to gen-idea, which didn't resolve anymore and isn't needed, since IDEA 14 supports build.sbt - based projects better than it used to with gen-idea in previous versions
2. updated scalatest to 2.2.1, fixing the deprecated code
3. updated scala to 2.11 and added the parser combinators module and fixed the deprecated code
4. removed the .idea and .idea_modules directories which weren't necessary and actually messed with IDEA a bit

Now all the libraries are up-to-date and to open the project in IDEA one just needs to go to File -> Import Project... and browse to build.sbt. Everything should work straight out-of-the-box, unit tests included.

This could probably be done in less than 5 commits, but I didn't want to waste time squashing, reverting and so on...