Fixed various dependency issues:
 * Properly changed all artifacts of rxjava-core to be rxjava-x.y.z.*
 * For Groovy/Clojure/JRuby/dynamic, moved dependency on rxjava-core to provided scope, as well as all tests
 * For Scala, left rxjava-core as compile scope, since rxjava-scala jar doesn't contain Observable (as constructed)