Bump pillow from 5.3.0 to 6.2.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.3.0 to 6.2.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](https://github.com/python-pillow/Pillow/compare/5.3.0...6.2.0)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,5 +1,5 @@
 pyowm==2.10.0
-Pillow==5.3.0
+Pillow==6.2.0
 ics==0.4
 feedparser==5.2.1
 pytz==2019.3