ekmett/lens — pull request #311 by bennofs (2013-06-17 16:27:16+00:00)
Title: Add Monoid and Semigroup instance for Accessor

Added a Monoid and Semigroup instance to Accessor. This allows to write for example:
``` haskell
> [1,2] ^.. (ix 1 <> ix 0 <> ix 3)
[2,1]
````
This is my first pull request to lens, so let me know if I did anything wrong.