Update exception_notifier gem

We need this for compatibility with Rails 4
Update gems for Rails 4.0.2
Update config to be compatible with Rails 4
No more assets group in rails 4

We use pre-compiled assets anyway.
Update associations to use new syntax
/script/rails is unnecessary

Rails and Bundler should just do the right thing
Initialize new secret token setting
This should no longer be necessary
scoped method deprecated
TEMP: Disable protected attributes

They don't play nice with Rails-4 compatible globalize. Will replace
with strong params where appropriate.
Use Rails 4-compatible gds-sso branch

Current release breaks unless you have protected_attributes
Confirm is now a data attribute
Disable implicit join references

This gets rid of deprecation warning relating to referencing an eager
loaded table in an SQL snippet. Because we don't rely on implicit join
references, we can just disable the feature entirely.
Don't call #all on associations - use #load

Another Rails 4 deprecation
Replace old-style dynamic finder

This replaces old-style dynamic finders that have been deprecated and
also some that don't play nice with the Rails-4 compatible globalize
gem - dynamic finders on translated columns don't work.
Update friendly_id config

Note that this version of friendly_id has a couple of differences to
the previous version:

1) The default sequence seperator used when there is a slug clash is
now a single '-', rather than a double-dash that was used previously.
I've left the config to use the new single-dash, but this can be set
back to double-dash if we deem this necessary.

2) Previous versions of friendly_id appended a numeric sequence to
make slugs unique. The numeric sequence has now been replaced with a
UUID (to simplify the code and make it more thread-safe).

This second change results in very ugly slugs. However, friendly_id
provides a new mechanism to reduce the chance of such clashes by
allowing you to specify slug candidates (see
lib/friendly_id/slugged.rb in the friendly_id gem). I'll explore using
this in a later commit.
Stop HtmlAttachment slug generation complaining

friendly_id doesn't like generating slugs for HtmlAttachment because
the scope it gets given is on the base Attahment class, and that hasn't
had the necessary friendly_id helpers mixed into it. By forcing the
scope to one on the HtmlAttachment class itself, we keep friendly_id's
slug generator happy and also tighten up the slug scopping so that
html attachments' slugs are scoped to the owning document.
TMP - validations on join models...

Some change in either the way ActiveRecord or FactoryGirl works has
resulted in these validations stopping the factories from working.
I'm temporarily disabling them here to get the build further towards
green.
AR#model_name now returns an object

Can't just treat it like a string.
Remove no-longer-necessary workaround

ActiveRecord now does the right thing.