Broke down reactor-groovy module to two separate ones so Intellij Idea could compile them. Issue was due to usage of extensions from same module.
Added configuration to ide.gradle to add optional libs into Idea Provided scope making compilation from Idea possible.
Merging PR #307 Breaks out Groovy extensions into their own submodule so they can be compile separately (and first) to ensure they're available to other submodules. IDEA seems to have issues with them if this is not done in this order.

Also bumped versions in the Gradle build and am now using Java 8 to build with.