added link to title in map popup. Fixes #115.
[refs map] Uses title case for map popups
Merge pull request #132 from codefordurham/map

Added link in the map popup
Prevents the importer from overwriting the property_id field
Merge pull request #137 from codefordurham/api_import_fixes

Prevents the importer from overwriting the property_id field
Import only recent changes
Added new management command to do incremental imports only

* Much faster imports from Durham County due to incremental nature of the data
* Rewrote some of the API code for better clarity
Added celery task to run incremental updates
Pep8 fixes.
Changes suggested by Victor