Bump pillow from 5.1.0 to 6.2.0 (#65)

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.1.0 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/5.1.0...6.2.0)

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

requirements.txt

@@ -1,6 +1,6 @@
 discord.py>=1.1.2
 beautifulsoup4==4.6.0
-pillow==5.1.0
+pillow==6.2.0
 numpy==1.14.3
 youtube_dl
 emoji>=0.5.2