add GetVersion to the API

[BenTheKlein]

just like in raven-python https://github.com/getsentry/raven-python/blob/master/raven/init.py#L37

[Horaddrim]

Okay, I think I can start with that one! Maybe put the good first issue label?

[mattrobenolt]

@Horaddrim Added :)

[Horaddrim]

Just to make sure, this VERSION variable in the Python code, is the SDK version right?

[mattrobenolt]

Correct.