Move named value access under consistent namespace
Add const mutator
Update flay threshold
Rename Assignment as VariableAssignment
Change variable interpolation into simpler to read statement
Add constant assignment mutator
Update flay threshold
Update spec to not capitalize the random string

* Allow the library code to handle this, to test that it is properly
  upcasing whatever is returned.
Merge pull request #71 from mbj/const-mutator

Const access and assignment mutators