Tiny documentation update

Update 'edx' group to 'adm' group in LMS setup

* Use the 'adm' group for permissioning assets needed during LMS
  initialization, because ubuntu doesn't have the edx user until it logs
  out and logs back in.

Add site-specific parameterization for nginx config

Update permissions on git identity files

* Add ubuntu to edx, restrict git identity access to edx group members

Updating mitx repo location

mitx is now in the edx org

bugfix install of example user (needed secure_dir)

Coudformation refarch template: fix elasticache creation output

cloudformation template changes for outbound SSH, internal DNS names

npm install  playbook

change directory structure ascii art to reflect current status (secure_example)

Refactor how we manage secure data, git-identity changes

* I've moved the example secure directory to playbooks/secure_example,
  the directory structure in your secure repo should mirror that in
  secure_example/
* If you run the lms role without a valid git-identity file it will
  fail, there is an empty file checked into the secure_example dir
* Using GIT_SSH env for git checkout, we will also need to use that
  for pip installs that use git if there are private repos in
  requirements.

You may want to deploy more app instances by default to start with.

It's a bummer that enabling VPC DNS hostnames isn't supported by
CloudFormation yet, so we have to do this manual command hack like
we're already doing for ElastiCache. Helpful bit for configuring your
ssh as well.

Install debian and python dependencies for LMS/CMS

* Move debian package list to roles/lms/vars/main.yml
* Move lms_git_repo to roles/lms/vars/main.yml

Return private DNS names that will be resolvale within the VPC. This way
we can define a general SSH config that will work for all hosts.

Some minor ruby role changes

high-level overview of ssh config

moved creation of /opt/www and www user into ruby role

Need to be able to ssh *out* of our hosts to communicate with GitHub for
private repos. Add egress TCP port 22 access to the NATSecurityGroup.

* Cleanups in LMS task
* Add missing debian packages: libgeos-dev, nodejs
* Alphabetize list of debian packages in LMS task