Ensure Curry Repository attributes are not null

This enforces non-nullable Curry::Repository attributes at the database level.
Merge pull request #622 from opscode/not_null

Ensure Curry Repository attributes are not null
Paginate all, individual and company contributors

The contributors lists are getting a bit long and costly when rendering
the page so let's paginate them.
ApplicationController always 404s with HTML
Handle missing templates with 404s
Add utf8-cleaner gem

If you make a request to Supermarket with invalid utf8 params it will
raise an exception because of a Rails bug explained here:
http://dev.mensfeld.pl/2014/03/rack-argument-error-invalid-byte-sequence-in-utf-8.
The utf8-cleaner gem sanitizes invalid utf8 strings preventing these
exceptions.
Merge pull request #623 from opscode/missing-template-exceptions

404 with HTML by default
Refactor follow/unfollow button AJAX

Rather than re-rendering the entire view and manipulating the dom upon a
successful follow/unfollow request this moves the follow buttons (for
the show view and the partial) into a partial and renders them upon a
successful follow/unfollow then inserts the results into the dom.
Refactor User.authorized_contributors to return an AR Relation

So the result of User.authorized_contributors can be paginated using
Kaminari's SQL pagination refactor User.authorized_contributors to
return an ActiveRecord::Relation instead of an Array.
Merge pull request #625 from opscode/utf8

Add utf8-cleaner gem
Merge pull request #626 from opscode/follow-button-refactor

Refactor follow/unfollow button AJAX
Make copy for version downloads clearer

We currently display the number of downloads for the current version
being viewed so we should make the copy more clear to convey that.
Remove usermenu z-index

The z-index for the usermenu is no longer needed and it is causing a bug
when modals are open so this removes the z-index declaration.
Add delimiters for large download counts
Merge pull request #631 from opscode/cookbook-versions-count

Make copy for version downloads clearer
Merge pull request #624 from opscode/paginate-contributors

Paginate all, individual and company contributors
The ApplicationController should always respond with HTML

The respond_to block would respond to JSON requests with the HTML text,
but this would not be rendered in the browser. We definitely want the
HTML to be rendered
Be explicit with follow button show partial render

Fixes issue where the CookbookVersion#show was 404ing.
Merge pull request #636 from opscode/template-error-qa

The ApplicationController should always respond with HTML
Merge pull request #637 from opscode/follow_partial_fix

Be explicit with follow button show partial render