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
Started work on page duplication
Renamed 'duplicate' to 'copy'
Implemented recursive copying
Page copy now copies child objects
Fixed bug causing child objects of child pages to not be copied
Minor cleanup
Make sure we have the most specific version of a page before copying child objects
Changed **kwargs to update_attrs
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'