Refactor :order clause to model scope
First attempt API V1, quotes controller

Thanks to http://railscasts.com/episodes/350-rest-api-versioning
Fix quote creation issue in spec

- Unmatch attribute in factory fixture
- PublicActivity configuration nil check
Add gem 'rspec-json_matcher'
Implement very skeleton api of quotes :index, :show
Enable :focus metadata to run focused specs
Add 'active_model_serializers' gem
Disallow root element for ActiveModelSerializers
Generate Quote < ActiveModel::Serializer
Add iso8601 formated :created_at to QuoteSerializer
Embed user into quote body
Add todo to include avatar_url in embed user
Introduce a new class UserAvatarUrl

The overall logic to fetch user avatar is still too messy, but at
least this allows us to embed user avatar url in API easily!
Merge pull request #31 from kinopyo/api_v1

Api v1, supports quotes #index and #show