Bump Scala version to 2.10.1, workaround for broken for-comprehension

See <https://gist.github.com/vmarquez/5106252/> and the mailing list thread
<https://groups.google.com/d/msg/scalaz/FqCWOmSEwUY/cchJirGmbeYJ>.
Revert "add arbList method for fix xml test in Scala2.10.0-RC5. see #231"

Fixed in 2.10.1-RC2.

This reverts commit 1bac54c420356d84eaae31702cd6605550114aae.
Remove some unused variance, with a little remaining breakage in Free.
Backtrack a lot; scalac tricked me.
Avoid illegal variance in bitraverseImpls.
Avoid illegal variance in traverseImpls.
Remove more unused variance.
optimize NonEmptyList foldMap1 (avoid StackOverflowError)
correct comments and boolean functions of nand and nor functions. Correct syntax to call to correct functions.
Merge pull request #332 from xuwei-k/NonEmptyList-foldMap1

optimize NonEmptyList foldMap1 (avoid StackOverflowError)
Merge pull request #339 from AlecZorab/fix-boolean-functions

Fix boolean logic functions.
tweak README

[ci skip]
Fixes #180: include SBT config in README

[ci skip]
nuke deprecated classes and methods
Fix Equal[Map[K, V]] instance.

Fixes #341.

Checks corrects keys set.
Swapped to using total 'get' function on map. Map.apply, urghhh!
instructions for using Scalaz with other build systems

[ci skip]
Switch 'default' scala version to 2.10.x.

Reasoning:
 - Compiler fails a _tiny_ bit less frequently.
 - Will force the issue on the 2.10 warnings.
Merge pull request #296 from larsrh/topic/2.10.1

Bump Scala version to 2.10.1
fix MapTest
Merge pull request #343 from xuwei-k/fix-MapTest

fix MapTest