renaming cellLoad to cellPeek, fixes #176
renaming cellStore to cellPoke, fixes #176
Merge rename cellLoad/cellStore to cellPeek/cellPoke fixes #176

- This better reflects the naming because we are mainly concerned with
  Storable types and not EndianStore types.
Moved initialize and finalize to Memory from Gadget to new classes.
Added defaultCxt in Hash type class
Sha family of hashes fixed for change in memory interface
Fixed Blake for change in memory
Fixed Hash Tests
Fixed Hash Benchmarks
Ciphers fixed for Memory interface change
Cipher tests fixed for memory interface change
Fixed raaz-random for memory interface change
Fixed raaz-modular for memory interface change
Renamed cellLoad and cellStore to cellPeek and cellPoke in the patch
Merge new memory interface

- Gadget memories now has the job of initialisation and
  finalisation.

- Simplifies the implementation of many related primitives.