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)
update package object comment
Merge pull request #333 from xuwei-k/scaladoc-package-comment

update package object comment
Bump the test timeouts on TimerTest up to 5 secs to see if that rids us of the odd test failure.
Merge pull request #336 from seanparsons/future-test-timeout-bump

Cranked the test timeouts on TimerTest up to 5 seconds.
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]