Set correct tested version for scripted tests
Allow overriding default sbt-idea settings.
Add test for #211
Update readme
Set language level according to scala version used by the module (#195)

Conflicts:
	src/main/scala/org/sbtidea/IdeaProjectDomain.scala
	src/sbt-test/sbt-idea/dependency-with-classifier/.idea_modules/main.iml.expected
	src/sbt-test/sbt-idea/external-rootproject-dependency/.idea_modules/dependency-root.iml.expected
	src/sbt-test/sbt-idea/external-rootproject-dependency/.idea_modules/root-project.iml.expected
	src/sbt-test/sbt-idea/simple-project/.idea_modules/main.iml.expected
	src/sbt-test/sbt-idea/with-integration-tests/.idea_modules/main.iml.expected