Updating Gemfile and lock

Updating to point at newest Rails gem

Updating lock to point at new sources
Updates to README

- linking to Concepts page

- updating Rails-steps to set ENV variables before running Rake tasks

- fixing incorrect account-verification link in Rails README

- fixing incorrect password reset token-verification link in Rails README

- changing special group-name from "admin" to "foo"

- changing ENV variables used in Sinatra app to match those in Rails app