Fixed conjugate gradient search

Modified conjugate gradient code to use Nonlinear Conjugate Gradients with Newton-Raphson and Fletcher-Reeves, as described in sec B4 of Jonathon Shewchuk's "An introduction to the Conjugate Gradient Method Without the Agonizing Pain".

Made CG ascent primary, getting rid of double negation.
Added doctests
Merge pull request #27 from cscherrer/master

Fixed conjugate gradient search
guard module annotations
disable full-laziness in the AD modes that rely on unsafePerformIO. GHC
7.8 is much more aggressive about inlining their bodies.
Update Composition.hs to correct a typo

small mistake in making ComposeMode an instance of Enum typeclass
pred succed
Merge pull request #30 from syllogismos/master

Update Composition.hs to correct a typo
Update README.markdown to reflect changes in an earlier commit.

tensors were changed to jet in an earlier commit. https://github.com/ekmett/ad/commit/3e52341a22c2b9482f581f866dff02feba28fa1a
Merge pull request #31 from syllogismos/master

Update README.markdown to reflect changes in an earlier commit.
Restore the AD type to derive Num, etc. instances independently from choice of Mode. This fixes the broken tests.
Add missing CPP pragma in Numeric.AD.Internal.Forward