Removed common/atomic, instead using std::atomic
Removed the need for X11 on OS X

It only causes issues when someone (who doesn't need it) doesn't have it.
Merge pull request #89 from archshift/X11-OSX

Removed the need for X11 on OS X
Merge pull request #88 from archshift/remove-atomic

Removed common/atomic, instead using std::atomic
Removed common/std_xyz, instead using the std header