Improve function comments by making them more tomdoc-like
Improve tracking of active stubs
Add stub_called function
Add stub_called_times function
Add stub_called_at_least_times function
Add stub_called_at_most_times function
Long lines are evil, make them short
Change when called state is reset

This allows checking if a stub was called even after it's been restored
to it's original. Called state is only reset when a new stub is created
for the same command.
Update readme
Bump version to 0.3.0