using vtalbot/markdown for markdown rendering
change order of inclusion
posts model, basic posts controller and routes
update database migration, group_id should be allowed null
basic post functionality
Merge branch 'feature/posts' into develop

* feature/posts:
  basic post functionality
  update database migration, group_id should be allowed null
  posts model, basic posts controller and routes
  change order of inclusion
  using vtalbot/markdown for markdown rendering