Add .get method to StateT

[ceedubs]

This gets the input state without modifying the state component.

[codecov-io]

Current coverage is 89.34%

Merging #875 into master will not affect coverage as of 70f3168

@@            master    #875   diff @@
======================================
  Files          169     169       
  Stmts         2337    2338     +1
  Branches        75      75       
  Methods          0       0       
======================================
+ Hit           2088    2089     +1
  Partial          0       0       
  Missed         249     249       

Review entire Coverage Diff as of 70f3168

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[adelbertc]

👍

[mpilquist]

👍