Raise error on unsupported options

Theis will be usefull to eliminate all
the possible confusion going on what options
are and are not supported by chronic.

One such example is:
https://github.com/mojombo/chronic/issues/182#issuecomment-47094623

It is a good idea to tell people know about it in advance
if they provide invalid or unsupported options.
Merge branch 'validate_options' of https://github.com/dnagir/chronic into beta