Merge pull request #132 from ruby-concurrency/actress

Adding features to Actors
JavaExecutor#wait_for_termination now honors a nil timeout (wait forever).
Merge pull request #138 from ruby-concurrency/wait_for_termination

JavaExecutor#wait_for_termination now honors a nil timeout (wait forever).
Bumped version number to 0.7.0.rc2
Fixed problems preventing C extensions from building on some platforms.
Improve comment wording
Merge pull request #140 from obrok/patch-2

Improve comment wording
doc update
Updated README
Wait for all children to terminate