build against 2.9.3
added uncurried versions of foldRight1 and foldLeft1 to Foldable1Syntax
Profunctors.
Fixed MVar retry behaviour.

Shadowing for the loss. When retrying it incorrectly
used the last value it saw rather then the value it
was attempting to write.

Fixes #314.
Added note to MVarTest.
add `Profunctor` to `GenTypeClass`; tuned
disable test for `Traverse[Zipper]`, since it causes memory leaks
Covariant @@
Merge branch 'scalaz-seven' of https://github.com/scalaz/scalaz into scalaz-seven
Added an empty Promise
remove redundant (and commented) instances