Fixed problems preventing C extensions from building on some platforms.

Released v0.7.0.rc1 (Release Candidate 1).

Fixed post-merge problems with Travis CI and buld tasks.

Merge pull request ruby-concurrency#100 from ruby-concurrency/actress

Actress post release fixes

Released v0.6.0

Prerelease 0.6.0.pre.2

Prerelease 0.6.0.pre.1

Released v0.5.0

Release pre-release update v0.5.0.pre.1

Released v0.4.1