68191444 Order of content plans

- set order as ref_no asc for all displayings of content plans
- did small clean up of code - corrected some controllers to use decent_exposure
70425858 display assigned tasks in user's profile

https://www.pivotaltracker.com/story/show/70425858

- added displaying of assigned tasks on user's profile page
- covered profile page with Rspec tests
Merge pull request #58 from bitzesty/68191444-content-plans-ordering

68191444 Order of content plans
Merge pull request #59 from bitzesty/70425858-user-profile-add-assigned-tasks

70425858 display assigned tasks in user's profile
70426360 task completion notification

- added Task mailer
- added Tasks::Complete interactor
- covered with Rspec tests
70513102 performance of contents index pages

- ContentPlans index page tweaks:
  - added eager load for tags (act_as_taggable_on's tag_list ignores .includes(:tags))
  - corrected fetching of contents sum of sizes ( contents.sum(:size) ingnores .includes(:contents))

- Contents index page tweaks:
  - set fetching of tags and users via eager loading
69450886 Comments added line breaks

https://www.pivotaltracker.com/story/show/69450886
Merge pull request #62 from bitzesty/70513102-performance-for-index-pages

70513102 performance of contents index pages
Merge pull request #63 from bitzesty/69450886-comments-line-breaks

69450886 Comments added line breaks
Merge pull request #60 from bitzesty/70426360-email-about-task-completion

70426360 task completion notification
70426668 Task overdue notification

- added overdue tasks notification mailer
- setup whenever, added cron task
- covered with Rspec tests