Modifiying vagrant to make an easy dev env setup

Setting up answers should not require anything more than a `vagrant up`
or `foreman bootstrap`. These changes will add the required libs and
recipes to chef so the answers platform is running in the dev env
within the VM.
Move postgres user data to an encrypted databag
Move rails env and ruby version to attributes
Generate secret files using encrypted data bags
Set memory in Vagrantfile using an ENV variable
Add bootstrap script for easier setup
Add swap space to help with initial compilation
Use chef's notification system to restart ES

The initial provision was failing becuase the ES reindex was running
before ES was started. This should force ES to be restarted before
running the reindex.
Update readme to include instructions for vagrant
Follow the convention for naming AWS env vars
Merge pull request #175 from 18F/feature/easy_dev_env

Modifiy vagrant to make for an easier dev env setup