Remove rb-readline which is no longer needed.

This was causeing errors in the console. Although the errors can be
fixed by removing the require statement*, I removed the gem entirely as
it is no longer directly needed by our app.

* https://github.com/luislavena/rb-readline/issues/93
WIP: need to fix error w/encrypted booleans.
set marshaling config even though it should be set to true by default.
improve flexibility of yes_or_no helper method
add concern for shared encryption code. cleanup profile constants.
remove redundant constant names in Profile. + test for encrypted attrs.
add tests for encrypted profile attributes