Bump cython from 0.29.6 to 0.29.7 (#90)

Bumps [cython](https://github.com/cython/cython) from 0.29.6 to 0.29.7.
- [Release notes](https://github.com/cython/cython/releases)
- [Changelog](https://github.com/cython/cython/blob/master/CHANGES.rst)
- [Commits](https://github.com/cython/cython/compare/0.29.6...0.29.7

)

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

requirements.dev.txt

 flake8==3.7.7
-Cython==0.29.6
+Cython==0.29.7
 nose==1.3.7
 pylint==1.9.4
 pytest==4.4.0