Fix width and height bug

This resolves a bug where if you didn't define a height or width in the tag, it would result in a console error.
Also adds some fixes to the readme's formatting.

Thanks to @allanwhite and @potentweb for the fixes!

Version 2

– Completely refactored the code base, making it easier to maintain and more stable.
– Changed the param for classes to class [BREAKING]