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.
Use Rails 4.1.8
Convert to Bash

According to shellcheck, the `&>` used on line 10 is not standard POSIX
shell.
Use bin/setup from Travis

In order to test the executable documentation provided by bin/setup, we
should use bin/setup from CI.

Anything that is inappropriate for a CI environment is tucked behind a
check for the CI environment variable, which is present on Travis,
Circle, TDDium, etc. We should strive to mimize what's in here.

This necessitated breaking up the single call to `rake dev:prime` (which
has `db:setup` as a dependency) into a call to `rake db:setup` followed
by a later call to `rake dev:prime` if we're not in CI.

A change was also made to the foreman installation. It wasn't clear to
me why we needed to error when Foreman wasn't installed when we could
just as easily install it.

I transitioned checks for gem presence to use `gem list --installed` and
to omit the `--no-document` flag. This flag should be decided by the
user's `.gemrc`.
Don't install Foreman as a gem

Including it in the Gemfile prevents us from using the version from the
Heroku toolbelt, because the one on bin or rbenv's shims will override
/usr/bin or /usr/local/bin.

As much as possible, we think it's good to restrict bin/setup changes to
the project. The big exception for most projects is bundle install.