Add ability to specify custom python requirements.

This lets you specify additional python packages to be installed
into the edxapp virtual environment.

The `EDXAPP_EXTRA_REQUIREMENTS` should be a list of dict objects
with `name`, `version` (optional) and `extra_args` (optional) keys,
that correspond to the options of ansible's pip module.

Example:

    EDXAPP_EXTRA_REQUIREMENTS:
      - name: mypackage
        version: 1.0.1
      - name: git+https://git.myproject.org/MyProject#egg=MyProject
adding libfreetype6-dev
Merge pull request #1540 from edx/han/libfreetype6-dev

adding libfreetype6-dev to release
New base AMI, updating AMIs for Ubuntu
Merge pull request #1563 from edx/han/release-sandbox-ami

New base AMI, updating AMIs for Ubuntu
Use boto 2.32.1
make jump box specifiable and overridable
Upgrading S3 pluging to 0.6
Clean up based on TODO.
Merge pull request #1615 from edx/feanil/env_update

Clean up based on TODO.
Set none as the default.

No one will have access to the fake default bucket causing
things to break if it isn't overridden.
Merge pull request #1616 from edx/feanil/xbfs_update

Set none as the default.
Move kibana nginx template to correct location
Merge pull request #1617 from edx/cg/mv_kibana_template

Move kibana nginx template to correct location
Merge pull request #1595 from edx/han/jenkins_admin

Upgrading S3 pluging to 0.6
Add port support for kibana configuration
For SSL, should have been SSL port
Merge pull request #1618 from edx/cg/add_port_to_config

Add port support for kibana configuration
Correct the syntax for the rabbitmq config file.
Correct the default settings for un-clustered mode as well.