Use Ruby 2.1.3
Change `File.exists?` to `File.exist?`

* `File.exists?` is deprecated in favor of `File.exist?`

https://github.com/ruby/ruby/blob/trunk/file.c#L1482
Evaluates Ruby on generating `en.yml` locale file

In order to evaluate the Ruby code `<%= app_name.humanize %>` in
`templates/config_locales_en.yml` introduced in 4b0b8c1

* Change `config_locales_en.yml` to `config_locales_en.yml.erb`
* Use `template` when generating `config/locales/en.yml` file instead of
  copying the template file
* Add spec to ensure `en.titles.application` is set to App Name
Don't add staging/production remotes w/o access

If user doesn't have access to staging or production Heroku applications,
they do not need/want to have the Git remotes created.

Real-world example:

https://github.com/codecation/trailmix/pull/123
Promote NewRelic gem to global group
Fix accidental indentation

I created this when editing the previous commit.
Update README to match placement of New Relic RPM
Move 12factor gem explanation into Heroku section
v1.18.0
Update to Rails 4.1.7
Bump Rails version in Gemfile.lock as well

Rails version were bumped in 03d2de2eef0c5b75f0724a472a391474508b85c3.
Turn off RSpec verbose mode by default

This prevents RSpec from printing the command that it runs when you run
rake, which clutters the screen.
Remove out-of-date documentation

https://github.com/thoughtbot/suspenders/issues/424
Use Ruby 2.1.4
Fix Bundler installation code

Our previous Bundler idempotency code did not work
if you had a version of Bundler installed on a different Ruby version.
Upgrade newrelic gem

* Specified version gives alert that newrelic "requires a security update for
  their Postgres explain plan support"
* Gem version was last set in July 2013: https://github.com/thoughtbot/suspenders/commit/8f133d2bd0f67097495a9c120f724754ef7b0285#diff-2b85b2e387999d51ca372ef132583e80
Improve memory of app on Heroku w/ New Relic

* Help avoid R14 (Memory quota exceeded) errors.
  http://forum.upcase.com/t/how-to-free-up-swap-space-heroku/3017
* Refactor away some duplication.
Use Heroku-recommended timeout numbers

Rename ENV variables to be very explicit.
Couples their names to their libraries.