Refactored code to be simpler to understand
Fixed occasional timing error in Selenium webdriver
Fixed issue #2703
Addresses issues in page cache implementation

Now uses CMS_CACHE_PREFIX for page cache version item to prevent clashing with other projects using same cache-backend. Also, avoids an issue where the master version could expire before entries cached against it due to the use of cache.incr() (which doesn't advance the TTL).
Merge pull request #2798 from jrief/fix-issue-2703

Fix issue 2703
Very small fix to docs, 'Extenstions' -> 'Extensions'
Merge pull request #2806 from jaywink/fix-doc-typo

Very small fix to docs, 'Extenstions' -> 'Extensions'
Merge pull request #2804 from mkoistinen/fix_page_cache

Addresses issues in page cache implementation
Merge branch 'develop' of github.com:divio/django-cms into develop