Added support for greater than two fonts.
Fixed #68
General style cleanups.
Travis integration
Added font caching
Minor syntax cleanup. Changed parameter of select_drawable_font() to const
Merge pull request #70 from graboy/master

Optional support for more than two fonts, fixed issue #68
Fix #69. Thanks @matchew !
Little documentation fix, closes #73
Small documentation update
Better alpha mixing, should produce correct results
Add pixel offset

Add a formatting command to offset the text position by a pixel amount.