Merge branch 'update_requirements' into 'master'

Update requirements

See merge request !327

requirements.txt

 Django>=1.10,<1.11
 django-localflavor==1.3
 Pillow
-django-compressor==2.1
-django-sendfile==0.3.10
+django-compressor>=2.1,<3
+django-sendfile<=0.4
 django-template-check>=0.3.0  # This should be in dev-requirements somehow
-bleach==1.4.3
-django-tinymce==2.3.0
+bleach>=1.5.0,<1.6
+django-tinymce>=2.6.0,<3
 pytz
-rcssmin
-djangorestframework==3.4.4
-django-ical==1.4
-django-libsass==0.7
-django-cors-headers
+rcssmin>=1.0.6
+djangorestframework>=3.5.3,<3.6
+django-ical>=1.4,<2
+django-libsass>=0.7,<1
+django-cors-headers>=2.0.0,<2.1