Fix milliseconds parsing

[d10xa]

print(dateparser.date.get_date_from_timestamp(u'1570308760263', None).microsecond)

0

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@952e79a). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #572   +/-   ##
=========================================
  Coverage          ?   95.21%           
=========================================
  Files             ?      302           
  Lines             ?     2507           
  Branches          ?        0           
=========================================
  Hits              ?     2387           
  Misses            ?      120           
  Partials          ?        0

Impacted Files	Coverage Δ
dateparser/timezones.py	100% <ø> (ø)
dateparser/freshness_date_parser.py	98.94% <ø> (ø)
dateparser/data/date_translation_data/nb.py	100% <ø> (ø)
dateparser/parser.py	98.89% <ø> (ø)
dateparser/utils/strptime.py	100% <ø> (ø)
dateparser/languages/locale.py	98.65% <100%> (ø)
dateparser/date.py	98% <100%> (ø)

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[Gallaecio]

I think you may be over complicating your implementation. I think it may be better to modify RE_SEARCH_TIMESTAMP to match the timestamp with capture groups for the different relevant numbers here (e.g. r'^(\d{10})(\d{3})?(\d{3})?$'), and work with the captured groups.

As for tests, you should be able to simply extend the existing test_parse_timestamp test with new inputs and outputs.

[Gallaecio]

Please, mind https://github.com/scrapinghub/dateparser/pull/572/files#r338457223

[noviluni]

Good job @d10xa ! 😄