Create Ambiance.xml

Source: http://www.omgubuntu.co.uk/2011/02/help-ubuntu-11-04-by-making-an-ambiance-theme-for-gedit/#comment-156245276
Create AmbianceDark.xml

Source: http://www.omgubuntu.co.uk/2011/02/help-ubuntu-11-04-by-making-an-ambiance-theme-for-gedit/#comment-156245276
Merge pull request #150 from waldir/patch-1

Create Ambiance.xml and AmbianceDark.xml