Pswadi/get users json

Describe your PR
Enabling json api for users. Also added email and role to the json output.
Updated gemfile to get latest sawyer gem.

/cc @zendesk/samson 

### References
 - Jira link:

### Risks
 - None
done


On Tue, Aug 26, 2014 at 7:15 PM, Jason Smale <notifications@github.com>
wrote:

> In app/serializers/user_serializer.rb:
>
> > @@ -1,6 +1,9 @@
> >  class UserSerializer < ActiveModel::Serializer
> > -  attributes :id, :name, :gravatar_url
> > +  attributes :id, :name, :email, :role_id, :role, :gravatar_url
>
> I would prefer just role_id
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/zendesk/samson/pull/63/files#r16754548>.
>