Add indexed variants to mapM and mapM_.
Add ifoldM, ifoldM', ifoldM_, ifoldM'_.
Add izipWithM and izipWithM_.
Remove trailing whitespace.
Change vector maintainer to libraries@haskell.org.
Add tests for indexed variants of monadic fold, zip and map.
Merge pull request #6 from archblob/mlindex

Add indexed variants of monadic fold, map and zip, see #5.