Add version check and tests

[mpacer]

Is this primarily to get us bootstrapped into having more tests in bookstore? Otherwise, could you say where we expect the version check to be used outside of the tests?

Note: if we were going to implement something pep440 checking (like what we have in nbconvert)… I could definitely see the criticality for having this kind of version number check.

for reference nbconvert has a utility create_valid_version https://github.com/jupyter/nbconvert/blob/06f3a90f6b7b578a78efe1f17138a4fea43fcfa5/nbconvert/_version.py#L5-L60

def create_valid_version(release_info, epoch=None, pre_input='', dev_input=''):
    '''
    Creates a pep440 valid version of version number given a tuple integers
    and optional epoch, prerelease and developmental info.
    Parameters
    ----------
    release_info : Tuple(Int)
    epoch : Int, default None
    pre_input : Str, default ''
    dev_input : Str, default ''
    '''

[willingc]

This was mostly to get us started. We can either close or merge. No strong preference either way.