Oj indent assumes Fixnum whereas JSON indent assumes a String.

Without this, some of our code receives this unhandled exception:

> ArgumentError: :indent must be a Fixnum.
	from (irb):13:in `dump'
	from (irb):13:in `dump'
	from /var/www/platform/shared/dashboard/bundle/ruby/2.1.0/gems/multi_json-1.9.2/lib/multi_json/adapter.rb:24:in `dump'
	from /var/www/platform/shared/dashboard/bundle/ruby/2.1.0/gems/multi_json-1.9.2/lib/multi_json.rb:138:in `dump'
	from (irb):66:in `to_json'
	from /var/www/platform/shared/dashboard/bundle/ruby/2.1.0/gems/hashie-2.1.1/lib/hashie/hash.rb:30:in `to_json'
	from /opt/rbenv/versions/2.1.2/lib/ruby/2.1.0/json/common.rb:223:in `generate'
	from /opt/rbenv/versions/2.1.2/lib/ruby/2.1.0/json/common.rb:223:in `generate'
	from /opt/rbenv/versions/2.1.2/lib/ruby/2.1.0/json/common.rb:394:in `dump'