allow parser to have callback for processing unrecognized options
improve docstrings a bit for new struct field
clean up docstring, remove negated condition, remove type declaration in test
put if-condition on one line
clarify docstrings for UnknownOptionHandler, and some style fixes
fix commenting style to include spaces
add newlines before if blocks
add whitespace in test
fix whitespace and comments in test
newlines style fix
Merge pull request #116 from mpobrien/unknown_handler

Add field for callback to handle unknown/unmapped options during parse