Library is partially non-compliant with semver spec

Breaking input: 0.0.0-0foo.1

Expected result:

>>> import semver
>>> semver.parse('0.0.0-0foo.1')
{'build': None, 'major': 0, 'patch': 0, 'minor': 0, 'prerelease': '0foo.1'}

Actual result:

>>> import semver
>>> semver.parse('0.0.0-0foo.1')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/dist-packages/semver.py", line 65, in parse
    raise ValueError('%s is not valid SemVer string' % version)
ValueError: 0.0.0-0foo.1 is not valid SemVer string

Per item 9, only numeric IDs cannot contain leading zeros – since 0foo is not entirely numeric, it may contain a leading zero.

[sirzooro]

Any update on this? We use git commit hash as a prerelease part, so sometimes we trigger this error too.

[tomschr]

Duplicate of #194 so closing.