Fix MacOS build.

Adds a build script for mac that can be used to run build on travis.ci.
Change travis build script to run Linux build by default again.

Comments on how to run the mac build are included
Fixes build on OSX 10.9
Use OSX on travis
Add switch for OSX 10.9
Merge pull request #834 from cheif/macosbuildfix

Fixes build on OSX 10.9
Revert "Use OSX on travis"

This reverts commit 80579c2c920251f1e98e695a3ba5f4d9573b55e3.
Merge pull request #833 from fifengine/macosbuildfix

Fixes the MacOS Build