Version fails if git isn't available on the default system path

[devjack]

Reproduced on a windows machine checking out code via sourcetree. Whilst running in a git tracked directory, the git executable isn't available via the default system terminal (not included in the path).

Expected Behaviour:

• EITHER: Return a valid v0.0.0-2 version, using 2 commits as the flag for no commits.
• OR: Throw fatal exception and have the client handle it.

Current Behaviour:

• Returns a 'command git not found' message from Gitver->version();