0.3.0 - Ability to generate functions from `Signature`

Functions can now be created from a Signature object, in addition to string signatures. This unlocks many useful use cases, among easily creating function wrappers. Note: the inner function that provides this feature is get_signature_from_string. Fixes #8

Improved design by getting rid of the regular expression parser to check parameters definition. This assumes that the compiler will correctly raise exceptions when a string signature is not correct, and that inspect.signature or funcsigs.signature works correctly at detecting all the parameter kinds and annotations on the resulting function. It seems like a fair assumption... Fixes #9.

See documentation page for details.