Allows floats to be converted, and sets default digits

Now you can either pass in how many padding digits you want, or not.
If none or 1, then it assumes no padding.

You can also pass in a float now, which is convenient when
converting from CSS % values and the like.
Adds examples of float conversions & default padding.
Merge pull request #11 from suranyami/master

Adds floats to be converted and default padding digits