Fixed a TODO in resource_spec by wrapping filter addition specs inside a context
Bumped up version of better_errors gem in Gemfile to improve code climate
add Coveralls to track test coverage
add coverage badge to README
added missing and fixed wrong german locales for comments
bugfix: apps no longer use the same namespace hash

This was a big issue when running tests, since this:
```ruby
app = ActiveAdmin::Application.new
app.namespace(:brand_new_ns)
```
Would end up creating `:brand_new_ns` in the main app, since our
settings module (which doesn't dup objects) was being used to create
the `namespaces` API.
cleanup
move setting inheritance into its own module

Also added missing tests for `ActiveAdmin::Settings`
Merge pull request #2313 from Daxter/bugfix/namespace-pollution

Bugfix: apps no longer use the same namespace hash
update README's Code Climate badge to show our grade
Mexican spanish messages added.

Created `es_MX.yml` file.
restored missing quotes
remove old DB migration for AA comments

Now when you create a new project with AA, only one DB migration is
used to create comments
bug fixes for AA Comments UI

+ fixes #367 regression by calling `to_s` on the namespace
+ fixes #2294 by applying queries to the passed object
+ disables eager load of polymorphic relationships for Rails 3.0 since they don't work
cleans up `active_admin_comments_for`
typo fix in CHANGELOG
make query method used for select filters more flexible

As per my discussion with @t-anjan in #1093
Added jquery-ui-rails as a dependency

Conflicts:
	activeadmin.gemspec

undoes 1d29474c489d558, to apply the full fix
limit support to Rails >= 3.2 and Ruby >= 1.9

#### Removed outdated version-checking conditions
Modules affected:
+ CSV parser
+ asset registration
+ class reloading in development

#### Removed 99% of our custom class reloader in favor of Rails reloading
Note: I removed the code that purges `app/admin` from Rails' `eager_load_paths`
since there were no bad effects of doing so. Only the code that does this for
Rails' `autoload_paths` seems necessary.

#### Gemspec dependencies updated
+ fastercsv removed
+ coffee-rails added
+ sass replaced by sass-rails
Strong Parameters support for Rails 4

Adds conditionals to the admin user generator, and to the AA Comments
model & controller to handle both Protected Attributes and Strong Paramaters

Also updates dependencies so the test Rails 4 app will at least bundle