Bug 1287975 - Update Django to 1.8.14 (#1708)

To pick up the admin XSS fix:
https://docs.djangoproject.com/en/1.9/releases/1.8.14/

https://github.com/django/django/compare/1.8.13...1.8.14

requirements/common.txt

@@ -10,7 +10,7 @@ whitenoise==3.2 --hash=sha256:13e5d6673c7c0805c73037b7745e027141a8e39c5b6ba669b6
 https://github.com/google/brotli/archive/v0.3.0.zip#egg=Brotli==0.3.0 \
     --hash=sha256:0e1e88c74b5a4c9c39123fe8adfdce6262c80524398367420475716389d70791
 
-Django==1.8.13 --hash=sha256:dad5da0cd7f3cca7da3ac42a19abba30f5cc10fae4976e474051e7085b4e95d1
+Django==1.8.14 --hash=sha256:1716747f7e0fbee6e2c1c0bcdb74307139d441a79eb4dcc97d206c615e1ded15
 
 celery==3.1.23 --hash=sha256:eaf5dee3becbc35c7754a2d4482d53bdf72ea3f85dd258525259983262081474