Use javascript_include_tag helper to include javascript

Use Rails helper to include javascript. Assets pipeline divides manifest into separate files if assets.debug is true
modularize the search method dropdown for the filter form
fix Rails 4 problem with form builder ("undefined method `upcase'")

In Rails 4, ActiveRecord::Base#model_name no longer returns a string, but an ActiveModel::Name object, see https://gist.github.com/brupm/4544950. Calling #to_s on this object is a Rails3-compatible workaround for this change.
Merge pull request #2215 from tank-bohr/master

Include JS in layout with rails helper
remove redundant set of tests

This code almost exactly mirrors the tests abve it. The only difference
being that this uses `button_html` while the other uses `label` when
dealing with `f.action`.

We shouldn't be testing Formtastic's public API, so I'm removing the
second set of tests.
add test to ensure that form attribute labels are translated

for #2012
fix HABTM select filters

Assuming Foo HABTM Bars, the below now works as you'd expect:
```ruby
ActiveAdmin.register Foo do
  filter :bars
end
```
use the form buffer!
better filter defaults

+ `filter :attr, as: :select` now plucks DB values by default
+ properly add default polymorphic filters
+ move common Formtastic overrides into a single module
Merge pull request #1928 from Daxter/1093-dropdown-for-habtm

[1093] HABTM Select Filters
Merge pull request #1 from gregbell/master

Pull upstream