Datetime month parser

[mathieudpnt]

Need to be able to parse datetime in format 17/5/2014 03:52, right now timestamp_utils does not take into account %-m format

[Gautzilla]

I think a regex like (1[0-2]|((?<!\d)[1-9](?!\d))) should do the trick.

You might want to add this kvp in the _REGEX_BUILDER dict:

_REGEX_BUILDER = {
    "%-m": r"(1[0-2]|((?<!\d)[1-9](?!\d)))",
}

And add a bunch of tests to make sure %-m correctly parses dates like 2016/5/12 and rejects 2016/05/12

[mathieudpnt]

closed with #326