Allow new filepath-1.4 for GHC 7.10.1RC3

See haskell/filepath@d039d5ae

Conflicts:
	haskeline.cabal

This simplies the installation with GHC < 7.6.

Fix TODO: messageState param not needed anymore

Use explicit forall syntax to avoid warning

This is currently just a warning in GHC HEAD, but ought to be fixed
nevertheless:

    Variable ‘m’ is implicitly quantified due to a context
    Use explicit forall syntax instead.
    This will become an error in GHC 7.12.

Changes to accomodate GHC HEAD/7.10

Signed-off-by: Austin Seipp <austin@well-typed.com>

base needed a major version bump due to AMP landing

Add a "forall" quantifier before rank-n-types

Add Eq and Ord instances to Completion.

Add support for transformers-0.4.0.0

This is for compatibility with GHC Trac #4426

The test file covers ghc-7.0.1 and above.

This lets Hackage pick it up automatically.