allow for http/https urls to render without media prefix
do not block on HTTP errors when fetching external JS/CSS
Fix hard-coded MEDIA stuff

Django 1.4 uses STATIC/STATIC_URL for static assets and MEDIA/MEDIA_URL
for uploaded files and things like that.

This adds an additional setting which switches jingo-minify to use the
STATIC settings. Doing it this way maintains backwards compatibility
with existing Django sites using jingo-minify, but lets new Django 1.4
based sites use it and have things in the right place.
Use Django's static finder if appropriate.

When DEBUG is true and the new USE_STATIC setting is set, let Django see
if it can find the static file. This allows files to be found that are
in 'project/app/static', instead of only the centralized static
directory.

This change really only effects development, but it prevents having to
run './manage.py collecstatic' after every change while in development.
Instead files static files will be updated as they are changed so edit,
save, refresh works.
Update CONTRIBUTORS.
Fix issues raised in review feedback

* django 1.4 is now a requirement
* JINGO_MINIFY_USE_STATIC defaults to True--specify False if you want
  the old ways
Fix hardcoded access to 'media' dir.
Hook up Travis.
Move VERSION/__version__ into __init__.py.
Update CHANGES.rst.
fix tests using bad path
Remove unused import from fabfile.
Use mtime for build ID in dev for debugging.

Using time.time() for a build ID in dev breaks Firefox's script debugger
(see in particular bug 783393). This replaces time.time() with a helper
that returns time.time() for remote scripts and the file's mtime for
local scripts.