Use urlify.js for slugs

Modified _editor_js.html to include the
django-admin/js/urlify.js in the list of
static javascript includes and changed
page-editor.js to use the URLify function.
Fixed typo on list documents template
Logout now redirects to login view instead of a harcoded url.
Changes for password reset form

Fixed the styling of the "Enter your email..." message.
When email was empty a 500 error was thrown - added check
and exception for that case.
Merge pull request #9 from spapas/master

Use urlify.js for slugs and fix type on list documents template
rationalised login/password pages to work better x-browser, while also stubbing out reusable styles for any page outside the admin that is to take a basic wagtail ui
better label on contrib PasswordResetForm to save duplicating with needless instruction
gravatars now are retina by default
When source image of an {% image %} tag is missing, output a broken link rather than dying completely
use custom Rendition model for file-not-found images where relevant
Check if EMBEDLY_KEY has been set

This will check if EMBEDLY_KEY has been set in settings. If not
it will return a nice error message instead of throwing a 500
error.
Modified embeds.py to make it work

The Embedly API was not working at all because the return
value of Embedly (client) offered the attributes in dictionary
style and not as an object. Now everything seems to be fine.
Explorer interface was cluttered by too many horizontal dividing sections in the header. 'Explorer' title has been dropped in favour of making the current section index page feel more like the title. breadcrumb also toned down
Some icon font use converted to REM due to IE9's incompetent understanding of pseudo-elements
Handle SQLite substr syntax

Addresses https://github.com/torchbox/wagtail/issues/11
Added multi-backend support into wagtail search. Added Database search backend
Merge branch 'master' of github.com:torchbox/wagtail
Search: Updated search handlers and tests to use get_search_backend
Search DB Backend: Don't ignore the fields parameter
Merge remote-tracking branch 'upstream/master'