Bump pillow from 5.2.0 to 6.2.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.2.0 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](python-pillow/Pillow@5.2.0...6.2.0)

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ numpy==1.14.5
 scipy==1.1.0
 cython==0.28.3
 h5py==2.8.0
-Pillow==5.2.0
+Pillow==6.2.0
 scikit-image==0.14.0
 keras==2.1.6
 jupyter==1.0.0