Unable to parse time with 9 decimals

[TorbenDyrby]

I have time with 9 decimals, e.g.
2015-06-17T13:44:47.609273374Z

I suggest the following change to gpxfield.py:
RE_TIMESTAMP = mod_re.compile(
r'^([0-9]{4})-([0-9]{1,2})-([0-9]{1,2})T :([0-9]{1,2}):([0-9]{1,2})'
r'(.[0-9]+)?(Z|[+-−][0-9]{2}:?(?:[0-9]{2})?)?$')

I know the remaining decimal(s) wont be used, but it is still better to be able to parse the time.

[tkrajina]

Fixed in 5255351 .