Remove unused factory library from requirements file

Author: gregmuellegger

requirements/pip.txt

@@ -52,7 +52,6 @@ mimeparse==0.1.3
 mock==1.0.1
 simplejson==2.3.0
 stripe==1.20.2
-factory-boy==2.4.1
 django-copyright==1.0.0
 django-formtools==1.0
 django-dynamic-fixture==1.8.5