Bump docutils from 0.12 to 0.16

Bumps [docutils](http://docutils.sourceforge.net/) from 0.12 to 0.16.

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

Author: dependabot-preview[bot]

base-requirements.txt

@@ -2,7 +2,7 @@ dj-database-url==0.5.0
 django-pipeline==1.6.14
 django-sitetree==1.10.0
 Django==2.0.13
-docutils==0.12
+docutils==0.16
 Markdown==2.5.2
 cmarkgfm==0.4.2
 Pillow==5.1.0