Set Sass-Rails Version

* I've gotten the error `undefined method 'environment' for
  nil:NilClass` on projects I've recently started with Suspenders.
* Upgrading the sass-rails version solves this issue.
Be less restrictive about sass-rails version

Per @derekprior's comment, we just need a minimum:

https://github.com/thoughtbot/suspenders/pull/303#discussion_r10825370
Bump to 1.9.1
fix small typo in unicorn.rb
Make it easy for developers to join Heroku apps
Enable SMTP/TLS in SMTP settings

Be more secure by default.

https://en.wikipedia.org/wiki/STARTTLS

Recommended by SendGrid, our usual email provider.

http://sendgrid.com/docs/Integrate/Frameworks/rubyonrails.html
Add rspec config to treat symbols as metadata keys with true values

RSpec output contained a warning when I ran the factories spec because
of the :factory tag; RSpec 2 expects a hash instead of a symbol. Adding
this line to the config quiets the warning, and allows behavior that
will be default in RSpec 3.
Bump to 1.9.2
Fix Delayed::Job <-> Rails 4.1 dependency conflict

Fixes:

    Bundler could not find compatible versions for gem "activerecord":
      In Gemfile:
        delayed_job_active_record (>= 4.0.0) ruby depends on
          activerecord (< 4.1, >= 3.0) ruby

        rails (>= 4.0.3) ruby depends on
          activerecord (4.1.0)

https://github.com/collectiveidea/delayed_job_active_record/pull/86
Correct has_gem_included? test helper

It was always looking for rails_12factor, it now uses the actual gem
name that is passed in and makes sure it is usable in a Regex.
Update to stable Rails 4.1