Adding monadic find: findMOf and ifindMOf

Added general shortcutting versions of these two functions to
Control.Lens.Fold
This is my first git push ever, so let me know if something is messed
up. I tried to match the style and conventions for findOf and ifindOf.

findMOf :: (Monad m, Iso s a)     -> (a -> m Bool) -> s -> m (Maybe a)
and
ifindMOf :: Monad m => IndexedLens i s a      -> (i -> a -> m Bool) -> s
-> m (Maybe a)
Need to add new functions to export list
Fix docs for Getting
Merge pull request #309 from gseitz/master

Fix docs for Getting
Add Monoid and Semigroup instance for Accessor
Add INLINE pragmas to Semigroup/Monoid Accessor instance
Merge pull request #311 from bennofs/master

Add Monoid and Semigroup instance for Accessor
Control.Lens.Setter: Fix doctest with different float implementations

Closes #310.
Add foldBy family of functions
Simplified condensing due to an API change in `split`.
Used equality witness to eliminate unsafeCoerce in tinplate.
Eliminated the rest of the unsafeCoerces in Data.Data.Lens.
INLINE Data.Data.Lens.mightBe.
Merge branch 'master' of github.com:ekmett/lens
Added Control.Lens.Cons examples.
INLINE
Added Control.Lens.Traversal.partsOf examples.
Alternative is good enough for failover.
Fix ifindOf docs typo.
Added Control.Lens.Traversal.singular examples.