servo: Merge #13562 - Move mako out of wptrunner required packages (from servo:jdm-patch-5); r=jgraham

There was a review comment about this in https://github.com/servo/servo/pull/13382#issuecomment-249453104 that was never addressed.

Source-Repo: https://github.com/servo/servo
Source-Revision: c10de40e4ea4430037ac9156cc2b5d31f92a7cd4

servo/python/requirements.txt

@@ -5,6 +5,7 @@ mozinfo == 0.8
 mozlog == 3.3
 setuptools == 18.5
 toml == 0.9.1
+Mako == 1.0.4
 
 # For Python linting
 flake8 == 2.4.1