Update CUSTOM_THEME.md

Updated link to custom.css file which is now in the flavor's folder. The old link was to this [location] (https://github.com/openplans/shareabouts/tree/master/src/sa_web/static/css).
Merge pull request #107 from aplannersguide/patch-1

Fixed broken link to custom.css file in documentation.
Update dependency version for django-proxy

Version 1.0.2 fixes an issue with passing the upstream content-length through the proxy. Django should handle the content length itself, since it may decide to return the content with a different encoding than the upstream server.
Hotfix: The Shareabouts map is breaking for people whose browsers don't send up a user agent
3.11.18
Use a specific place url for sharing instead of assuming window.location
Link survey response activity to a custom route
Scroll to the response specified in the url
- when the survey response is rendered and the panel is shown, look for the response element and scroll it into view
Merge pull request #121 from openplans/scroll-to-comment

Scroll to comment
3.11.19
Add get_item template filter for accessing dictionary values
3.11.20
Allow styling data based on zoom level
- Update the data layers each time the map zooms or a place is focussed
- Update the default config to use the map.zoom variable
Remove the need for focus_icon and focus_style
3.12.0
Make the list view optional via the config file
Fix comment
3.12.1
Merge pull request #123 from openplans/optional-list

Optional list
Add gzip and expires WSGI middleware