Added sitemap generator
Sitemap timeout can now be configured with a setting
Added tests for sitemaps
Merge branch 'master' into sitemaps

Conflicts:
	runtests.py
Added get_sitemap_urls method to page and use it in sitemaps
Added page_published signal
Fire page_published signal on moderation approval
Renamed 'page' argument of page_published signal to 'instance'

This is to give more consistancy with djangos built in signals
Added frontend cache purger
Added requests as a dependency
Fixes to the 'purger' module
Renamed 'wagtailfrontendcache.purger' to 'wagtailfrontendcache.utils'
Allow purging of subpaths of pages
Renamed varnish_url variable to cache_serve_url
Merge branch 'publish-signal' into varnish-cache-invalidation
Use page_published signal for cache invalidation instead of post_save
Added docs for sitemaps
Added docs for frontend cache purging
Merge branch 'master' into varnish-cache-invalidation

Conflicts:
	wagtail/wagtailadmin/tests/test_pages_views.py
Don't install unicodecsv on Python 3 and fallback to pythons built in csv library it it isn't installed.