Bump pygments from 2.2.0 to 2.7.4

Bumps [pygments](https://github.com/pygments/pygments) from 2.2.0 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](https://github.com/pygments/pygments/compare/2.2.0...2.7.4)

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

requirements.txt

@@ -31,7 +31,7 @@ pexpect==4.3.1
 pickleshare==0.7.4
 prompt-toolkit==1.0.15
 ptyprocess==0.5.2
-Pygments==2.2.0
+Pygments==2.7.4
 pyparsing==2.2.0
 python-dateutil==2.6.1
 pytz==2017.3