Move State to data package

[ceedubs]

This is a partial partial fix for #785. So far I've moved state but not free. There are several different types within the free package, so it might warrant its own package. However, State/StateT was just sitting in the state package by itself, so I've gone ahead and moved it (so it now parallels Writer/WriterT).

[adelbertc]

👍 once we have green light

[codecov-io]

Current coverage is 89.30%

Merging #835 into master will not affect coverage as of 3fc1cfe

@@            master   #835   diff @@
=====================================
  Files          168    168       
  Stmts         2319   2319       
  Branches        75     75       
  Methods          0      0       
=====================================
  Hit           2071   2071       
  Partial          0      0       
  Missed         248    248       

Review entire Coverage Diff as of 3fc1cfe

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[fthomas]

👍