Require 'json' to prevent an json/common from choking on JSON::State.

This seems to be a workaround for https://github.com/colszowka/simplecov/issues/249. The error is: 

~/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/json/common.rb:270:in `pretty_generate': uninitialized constant JSON::State (NameError)

It's worth noting, this may be caused by my version of ruby.
Created a secondary twitter strategy.

This allows you to have two different Twitter apps associated with a user of your application. The use case I encountered was: 

As a user 
I want to use a Twitter account to login to the app 
And I want to use a different Twitter account from which to post updates.
Merge branch 'feature/twitter-share-strategy' into develop