Reorder the monad transformers in the Idris monad to allow completion

Completion of names will require access to the interpreter
state. Unfortunately, the stacking order of the monad transformers didn't
allow this. This has been changed.

As a side effect, when get was used to access the state, it has been
consistently replaced with getIState.
Merge pull request #176 from david-christiansen/completion

Reorder the monad transformers in the Idris monad to allow completion