Add getOrAdd to Map
Merge pull request #688 from ceedubs/map-getOrAdd

Add getOrAdd to Map
Delete useless `some` and `none` from OptionT
Add some useful `none` and `some` methods to OptionT
Relax `some` and `none` constraint

Should only require Applicative, not Monad.
Merge pull request #692 from puffnfresh/optiont-some-none

OptionT some/none