Add collection serializer
Merge branch 'examples' into implement-pagination-examples

* examples:
  Inherit post and comment serializers from application serializer
  Use rails_helper instead of spec_helper for posts and comments acceptances
  Use V1 instead of Api::V1
  Update rspec doc api for versioning
  Use v1 prefix in the url for api versioning
  Generate rspec api docs
  Use post and comment root elements on specs
  Separate posts and comments seeds
  Fix rubocop warnings
  Add posts and comments to seeds
  Add posts and comments to examples branch after merge with master
Use collection serializer instead default array serializer
Add specs to check meta info on response
Generate api rspec docs