'Tells if this version is numeric (vs. a non-numeric version).  A
version will be numeric as long as the first section of it is,
even if it contains non-numerica portions.
Some numeric versions:
1
1.1
1.1a
1.a.1b
Some non-numeric versions:
develop
system
myfavoritebranch'

def isnumeric(self):

    return isinstance(self.version[0], numbers.Integral)
