`floatformat` template filter docstring changes:

 * Split example cases.
 * Corrected use with negative arguments (quotes are needed).
 * Added another example of a number that has decimal places that include a non-zero digit and that ends with zeros.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@6646 bcc190cf-cafb-0310-a4f2-bffc1f526a37