Add Traversable instance for ContVec

--HG--
branch : version-0.5
Add method to the Arity type class

--HG--
branch : version-0.5
Merge Arity into Cont module

--HG--
branch : version-0.5
Rewrite ContVec

Breaks build

--HG--
branch : version-0.5
Fix build

--HG--
branch : version-0.5
Really fix build and revert to old head

--HG--
branch : version-0.5
Update cabal file

--HG--
branch : version-0.5
Remove mkN

--HG--
branch : version-0.5
Use {i,}foldM defined in Cont

--HG--
branch : version-0.5
Remove unused function

--HG--
branch : version-0.5
Rename function

--HG--
branch : version-0.5
Missing INLNE pragmas

--HG--
branch : version-0.5
Formatting

--HG--
branch : version-0.5
Shorten hideLast

--HG--
branch : version-0.5
Doc

--HG--
branch : version-0.5