Drop support for Python 3.5, 3.6 versions

[codecov[bot]]

Codecov Report

Base: 98.23% // Head: 98.30% // Increases project coverage by +0.07% :tada:

Coverage data is based on head (807dc43) compared to base (0f5d9c5). Patch coverage: 100.00% of modified lines in pull request are covered.

:exclamation: Current head 807dc43 differs from pull request most recent head 6d9f97e. Consider uploading reports for the commit 6d9f97e to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1097 +/- ## ========================================== + Coverage 98.23% 98.30% +0.07% ========================================== Files 232 232 Lines 2604 2600 -4 ========================================== - Hits 2558 2556 -2 + Misses 46 44 -2 ``` | [Impacted Files](https://codecov.io/gh/scrapinghub/dateparser/pull/1097?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub) | Coverage Δ | | |---|---|---| | [dateparser/date.py](https://codecov.io/gh/scrapinghub/dateparser/pull/1097/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub#diff-ZGF0ZXBhcnNlci9kYXRlLnB5) | `100.00% <100.00%> (+0.71%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub)

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