* Create a global variable lms_source_repo to make it easy to update
  where to pull mitx from when mitx moves
* Create global variable venv_base to store location of edx virtual
  environment, defaults to /opt/edx
* Create edx virtual environment to store python modules
* Add tags to LMS and CMS tasks to make selective running and testing
  easier
* Install a long, static list of debian packages, which has been
  manually curated from other edx configurations; this probably needs
  more attention and in the future should probably be divided better
  among various roles.
* Install the list of python packages distributed with the mitx
  repository
* Install some really useful software, namely mosh and tmux

adding license

Feature/e0d/reference architecture

Feature/jbau/env parameterizaton

reduce scaling group minimums to 1 for dev/test

don't require 2 caches for dev/test cases

Eventually we might want to set these thresholds to have better ranges,
but for trying the stack out I say that we shouldn't require an more
than the minimum number of machines.

Also changed top level playbook ymlv var search to follow a path, first
over {{ secure_file_dir }} set in group_vars/all then at
vars/secure_default

parameterize availability zones; reformat templ maps

var empty, so no actual users are created

Added defaults to some of the settings to make it more likely that
someone will get a stack up and running on the first try: deployment
key and environment tag.

Parameterized the availability zones instead of hardcoding them to
us-east-1. Each region has it's own notion of what is primary and
what is secondary, etc. because it seems that not all capabilities
work in all AZ's.  Specifically I got this error when trying to
create a VPC in us-west-1.

> Value (us-west-1b) for parameter availabilityZone is invalid. Subnets
> can currently only be created in the following availability zones:
> us-west-1c, us-west-1a.

For us-east-1 "B" and "C" are still the primary and secondary so EdX
shouldn't be affected. But in us-west-1 primary=A and secondary=C.
We'll have to learn over time what works best for other regions.

Reformatted the mapping sections to make them easier to read.  Hope
you don't mind.  Much terser and easier to eyeball.

Terser overall description.  Removed the "you'll be billed!" warning.

Change made in other tempates, doing for this template too. At some
point there was a copy/paste error and the eu-west-1 was used for
us-west-1. See 2cba8413

Jrbl/feature/git checkout

* Replace hardcoded instances of /opt/wwc with $app_base_dir, which
  defaults to /opt/wwc.
* Add tags to nginx tasks so they can be selected independently.

* create_users creates an 'edx' group
* create_users task edited to put all admin users in adm and edx groups,
* create_users assigns all users a shell
* lms installs ssh keys for mitx checkout, creates target dir in
  /opt/wwc, and checks out the mitx source

change module->library, update the example playbook

By default ansible will load libs in library/ which means
you do not need to specify a module path if you are invoking
ansible from the playbooks/ dir.

Added some comments to the rolling example

Bugfixes/jbau/ami and sync hooks

Fixing names

Looks like there was a copy/paste error, the AMI's that were in there
before were the same as Europe.  These new ones work.

Implements simple rolling deploy logic.

Requires the latest ansible to use (you may need to remove and add it again if
you are in a virtualenv)

See `edxapp_rolling_example.yml`

A new module is necessary for ELB information since that is not
available in EC2 metadata (which is what ec2_facts fetches).

ec2_facts grabs the instance ids and other meta information
ec2_elb_facts fetches ELB information
elb_reg.py takes an elb and instance id and will either register or
deregister. (called as pre and post).

`Serial` should be set to the number of instances that you want to
operate on simultaneously, currently set to 1.

Feature/jarv/move vars to role

Adding pre-commit and post-checkout hooks

This keeps vars that are specific to roles with the role, not
very well documented except in the playbook example here:
https://github.com/ansible/ansible/blob/devel/examples/playbooks/roletest.yml

This makes playbooks more concise since you do not have to explicitely
include vars for each roles, var_files will still override any of the
default values in <role>/vars/main.yml

package installation will be managed by config management system, in our...

Jarv/multi instance

* Make git hooks always execute utilities relative to git repository root
* And make them fail if called from outside the git repository
* Make utilities save current directory and return after doing their
  things