Expose version parsing function

[chrisburr]

As requested by @petricm, exposes the version parsing regex as:

major, minor, pre, patch = diracCfg.parseVersion("v10r1p3")
assert major, minor, pre, patch == (10, 1, 3, None)

major, minor, pre, patch = diracCfg.parseVersion("v10r1")
assert major, minor, pre, patch == (10, 1, 0, None)

major, minor, pre, patch = diracCfg.parseVersion("v10r1-pre3")
assert major, minor, pre, patch == (10, 1, 0, 3)

[petricm]

Thank you. Can this be tagged once merged.

[chrisburr]

Done as 0.2.0! It should deploy itself to PyPI and conda-forge over the next hour or so.