* Set default padding chars to 0.5.
* Split num_padding_chars into num_label_padding_chars and num_value_padding_chars
to allow better control. Retain num_padding_chars as an input parameter, but
internally it is dropped.
* Remove padding multipliers.
* Add measurements image for developers. Helps show what each of the internal
measurements are.
* Add script to build example badges.
* Update example badges.
Reliability
===========
* Raise a value error if an invalid font is passed.
* Handle labels that are not passed as str.
* Raise a value error if an invalid color name is passed.
Testing
=======
* Expand doctests to increase test coverage.
* Add Arial size 11 font and extra font sizes (mainly for testing).
* Make parse_args and main more testable by taking args as an input parameter.
