Include getAPIVersion and getImplementationVersion

This includes the getAPIVersion and getImplementationVersion methods added
to SpongeAPI (SpongePowered/SpongeAPI#12).

The only quirk right now is that they both return the same value.

Signed-off-by: Steven Downer <grinch@outlook.com>
Merge pull request #13 from Grinch/master

Include getAPIVersion and getImplementationVersion