Sass Version Conflict: sass-rails vs. bourbon and neat

The latest versions of [Bourbon](https://github.com/thoughtbot/bourbon/blob/v4.0.1/bourbon.gemspec#L30) and [Neat](https://github.com/thoughtbot/neat/blob/v1.6.0/neat.gemspec#L25) require sass ~> 3.3, but Suspenders [doesn't specify a version](https://github.com/thoughtbot/suspenders/blob/v1.10.1/templates/Gemfile.erb#L6-L13) for either of those gems. Because of the lack of a version definition, new installations of suspenders have a conflict in the sass dependencies of both sass-rails and bourbon:

``` sh
Bundler could not find compatible versions for gem "sass":
  In Gemfile:
    sass-rails (~> 4.0.3) ruby depends on
      sass (~> 3.2.0) ruby

    neat (>= 0) ruby depends on
      sass (3.3.5)
```

This doesn't appear to be an issue in instances where earlier versions of the bourbon and neat gems were installed if they declared their sass gem dependency as `>= 3.2`.

Ultimately the problem is that sass-rails doest not yet support sass 3.3. While the sass-rails gem is [being rewritten](https://github.com/rails/sass-rails/pull/192), it might be best to lock the bourbon and neat dependencies of suspenders to those compatible with sass-rails.

([origin](https://github.com/thoughtbot/suspenders/pull/327#issuecomment-41419056))