Fix the required Django version

Since the commit fc3f018544c19b90cc63797d18970a4cc27ef2ad graphite-web requires Django > 1.4
Python 2.6 on Lucid doesn't like '{}.{}'.format(v1,v2)
Replaced with '{0}.{1}'.format(v1,v2)
Merge pull request #471 from dangarthwaite/fix_utils_empty_format

Python 2.6 on Lucid doesn't like '{}.{}'.format(v1,v2)
Merge pull request #438 from daccle/patch-1

Fix the required Django version
Make the default date format configurable.
Order the returned metrics alphabetically by name

Seems that when target metrics are retrieved from whisper using a *
operator.  The ordering seems to differ depending on the time span of
the data.