Add specs of Sequence #duplicate and #to_hash methods

[#55911802]
Implement Sequence #to_hash and #duplicate methods

[#55911802]
Fix one of the Sequence#duplicate tests

[#55911802]
Everything on this page should link to a sequence path.
On Sequence page: Click anywhere in the entire activity box to start.

https://www.pivotaltracker.com/story/show/72220290
Set correct positions of activities during sequence copying (+ tests)

[#55911802]
Update sequence duplication and tests

[#55911802]

- duplicate now accepts owner
- it uses transaction so we won't end up with partial duplication
  (we have lots of saving of various objects)
- tests reload object at the beginning, so they test if everything
  is really saved to DB.
Let authors duplicate sequences

Updated:
- cancan abilities
- sequences controller
- view

TODO:
- controller tests
whitespace mixups.
Fix for "Using the same activity in multiple sequences doesn't work."

https://www.pivotaltracker.com/story/show/72261558
Merge branch 'master' into staging

* master:
  Fix for "Using the same activity in multiple sequences doesn't work."
  whitespace mixups.
  Let authors duplicate sequences
  Update sequence duplication and tests
  Set correct positions of activities during sequence copying (+ tests)
  On Sequence page: Click anywhere in the entire activity box to start.
  Everything on this page should link to a sequence path.
  Fix one of the Sequence#duplicate tests
  Implement Sequence #to_hash and #duplicate methods
  Add specs of Sequence #duplicate and #to_hash methods