Update formula for 0.5.0
Remove unnecessary message
Merge pull request #6 from hido/upgrade-to-0.5.0-by-head

Update formula for 0.5.0
Upgrade to 0.5.1
Merge pull request #7 from hido/upgrade-to-0.5.1

Upgrade to 0.5.1
Modified to check Mac OS X's version first.

This change prevents installation of dependent libraries when attempted to install on unsupported OS X.