Bump pygments from 2.1.3 to 2.7.4 in /requirements

Bumps [pygments](https://github.com/pygments/pygments) from 2.1.3 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.1.3...2.7.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements/requirements.txt

@@ -42,7 +42,7 @@ pycparser==2.17
 pygal==2.3.0
 -e git+https://github.com/SrMoreno/pyst2@master#egg=pyst2
 python-crontab==2.4.0
-Pygments==2.1.3
+Pygments==2.7.4
 reportlab==3.5.34
 requests==2.12.5
 redis==3.5.3