Build C and C++ gitdate libraries

These expose some basic date parsing funcionality as C and C++
libraries.  I don't have any sort of mirror classes for C++ yet, but
it does at least appear to parse dates.
Add some simple date parsing tests

I just grabbed a date string from my email, passed it through "date -d
... +%s", and verified that this code spits out the same thing.  It's
not much of a test case, but I guess at least it's something!
Bump version to 0.0.1