Use replicateM instead of manual stateful initialization

Code becomes much clearer and ~30% more performant.
Vector 0.6 have this function.
Add instance for primitive vectors

/No vector is left behind/
Expose generic {de,}serialization functions

They are also renamed to match names from cereal-vector.
Longer names are less ambigious too.
Remove unused pragmas
Add -Wall flag to cabal file and switch off warning for orphans
remove cruft from .cabal file
Add benchmarks which were used to make performance claims