Generate random trees with management command

Example usage:
$ python manage.py random_trees --instance 1 -n 1000 -r 10000

Help:

$ python manage.py random_trees -h
Usage: manage.py random_trees [options]

Options:
  -v VERBOSITY, --verbosity=VERBOSITY
                        Verbosity level; 0=minimal output, 1=normal output,
                        2=verbose output, 3=very verbose output
  --settings=SETTINGS   The Python path to a settings module, e.g.
                        "myproject.settings.main". If this isn't provided, the
                        DJANGO_SETTINGS_MODULE environment variable will be
                        used.
  --pythonpath=PYTHONPATH
                        A directory to add to the Python path, e.g.
                        "/home/djangoprojects/myproject".
  --traceback           Print traceback on exception
  -i INSTANCE, --instance=INSTANCE
                        Specify the instance to add trees to
  -r RADIUS, --radius=RADIUS
                        Number of meters from the center
  -n N, --number-of-trees=N
                        Number of trees to create
  -d, --delete          Delete previous trees/plots in the instance first
  -p PTREE, --prob-of-tree=PTREE
                        Probability that a given plot will have a tree (0-100)
  --version             show program's version number and exit
  -h, --help            show this help message and exit
Add XYZ layer tiling code for tiles
Replace L with OL to make to clear we're using OpenLayers
Merge pull request #11 from ahinz/topic/tiles

Add XYZ layer tiling code for tiles
Merge pull request #10 from ahinz/topic/gen-random

Generate random trees with management command
Add Guardfile for auto change updates
Merge pull request #12 from ahinz/topic/guard

Add Guardfile for auto change updates
Add UTFGrid movement support

This is really just a sketch of how it would work. In particular, it
provides mechanics for adding a new interactive layer and relevant
callback.

So far the callback is sort of useless.
Merge pull request #13 from ahinz/topic/utfgrid

Add UTFGrid movement support