Add support for Gunicorn/Nginx

This changeset makes Gunicorn the application server for Django across
environments. In addition, Upstart handles launching the Gunicorn worker
pool and Nginx reverse proxies requests to it.

It is also important to note that when the application is provisioned in
the development and test environments, the Gunicorn `--reload` flag is
used. This provides automatic Gunicorn worker reloads when code changes
occur. I tested application reloading by making source code changes via
the Vagrant shared folder and worker PIDs changed as expected.

For more discussion, see: https://github.com/azavea/nyc-trees/pull/71
Enabling debugging support in development

In addition, I set `timeout` to 30 minutes and lowered it to 60 in the
`else` because the ELB terminates requests at 60 seconds anyway.
Remove references to `runserver`
Move gunicorn configuration to config file

This will make it easier to use the same config in multiple places
Add proof of concept script for gunicorn debugging
static -> collected_static (for now)
Move scripts to folder
Merge pull request #73 from azavea/feature/unicorn-nginx

Add support for Gunicorn/Nginx
Add support for selenium UI tests.

 - Add the ansible-git role for the app server, so we can install
   pip dependencies from github.com
Activate admin site
Merge pull request #76 from steventlamb/topic/add_admin_site

Activate admin site
Add flake8 checks to the test suite

This changeset adds `flake8` to the project test dependencies and
executes checks before the Django test suite. A failed `flake8` run
emits a known string ("flake8 check failed") so that the Jenkins text
finder plugin can mark the build unstable.

Attempts to resolve #70.
Add PostgreSQL command line client

This changeset installs the PostgreSQL command line client on the
application server so that it can be used to interact with the database.

Attempts to resolve #72.
Merge pull request #79 from maurizi/selenium

Add support for selenium UI tests.
Merge branch 'feature/hmc/flake8' into develop

Conflicts:
	src/nyc_trees/requirements/test.txt
Merge branch 'feature/hmc/psql-dbshell' into develop
Add support for pgweb in development

This changeset adds support for `pgweb` by installing the executable and
running it as a service. `pgweb` binds to `5433` within the VM and is
exposed to the Vagrant virtual machine host via `15433`.

Attempts to resolve #69.
Forward environment variables for Sauce Labs into VM
Support accessing the test live server (for Sauce Labs)
Add setting to allow LiveServerTestCase address to be changed

SauceConnect needs this to be accessible from more than just localhost