rm [frontend backbone] template caching

  - The only templates we fetch like this are wigdet edit templates
  - The templates are cleared on save
  - This means the only time we had a cache hit was when you do 'edit',
    'cancel', 'edit'. This almost never happens, and when it does, it's
    during development when you want a new template.

If there's a different use case in the future, this might be worthwhile
to put back, but it's useless code right now.
Add the ability to link to external pages

This allow buttons to link to external pages, and this centralize
external links.
Remove django-fusionbox dependency in setup.py
Move requirements file in demo site
Remove fusionbox internal fabfile
Remove django-fusionbox from requirements.txt file
Remove widgy.contrib.replacements module
Get rid of fusionbox.behaviors dependency
Remove fusionbox.core from the demo site INSTALLED_APPS
Remove dependency from django-fusionbox QuerySetManager
Add phonenumbers dependency to setup.py for PhoneNumberField
Copy PhoneNumberField into widgy

Signed-off-by: Antoine Catton <acatton@fusionbox.com>
Switch from django-fusionbox to django-argonauts
Get rid of fusionbox_tags dependency
Add salesforce's web to lead mapper
salesforce icons, shelfitem positioning updated
Fix button order
Merge pull request #75: Add salesforce's web to lead mapper
Remove double link registration
Use BeautifulSoup 4

BeautifulSoup import is the third version, which was a dependency of
django-fusionbox.