Add Const functor and const function

`const` function inspired by Runar's
[A Proper Constant Function in Scala](http://apocalisp.wordpress.com/2010/04/21/a-proper-constant-function-in-scala/)
blog post.
adding sequencef to foldable, sequence specialized on free
Add common instances for LiftIO and MonadIO
catchSome/Left + using for MonadCatchIO
formatting
fixed context bound for 2.9
fixing syntax.sequenceF_ to use Liskov instead of Leibniz as per Kenji's suggestion
Merge branch 'scalaz-seven' of https://github.com/scalaz/scalaz into scalaz-seven_sequencef
fixing a missing line, I'm learning about check-gen-type-classes!
put instances into the //// blocks for genTypeClasses
deprecate oddly-placed Kleisli and StateT effect instances
Merge pull request #663 from tpolecat/catchio

missing derived methods on MonadCatchIO
Merge pull request #658 from vmarquez/scalaz-seven_sequencef

adding sequencef to foldable, sequence specialized on free
Const.const s/Id/Function0, make ConstFunctions sealed
Merge pull request #657 from adelbertc/const

Add Const functor and const function
Merge pull request #661

Add common instances for LiftIO and MonadIO
Account for tighter definition of private in Scala 2.11.0-SNAPSHOT

SI-7475 fixed a hole in the the compiler, which does not allow:

	class C {
	  private def foo: Any = 0
	  def test(d: D) = d.foo
	}

	class D extends C

This was in line with:

> The private modifier can be used with any definition or declaration
> in a template. Such members can be accessed only from within the
> directly enclosing template and its companion module or companion
> class (§5.4). They are not inherited by subclasses,

Two choices here to comply: we could either ascribe to `==>[A, B]`,
which does have the member, or make it protected so it will be a
member of the subclass. I chose the latter in this commit.

Cherry-picking pull request #645 (e267458) from 7.0.x
Follow-up on 78ff758 for ISet
update to Scala 2.11.0-RC1