moved refinements to core_ext
removed refinements

We are now reopening the thread class
thread spec now uses respond_to
renamed thread.group to thread.eldritch_group

This is to prevent collisions with thread groups
renamed thread.task to thread.eldritch_task

This is to prevent collisions. It's a pretty common term, better be safe
removed ruby requirements from gemspec
Fixed readme to reflect 1.9 support
updated documentation for async methods with 1.9
updated travis config to support prior ruby versions and jruby