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.
Specify scala syntax for OptionT example
Make 'Type Class Hierarchy' example valid
Merge pull request #344 from bmjames/scalaz-seven

Minor Readme fixes
Merge pull request #328 from S11001001/topic/hk-ev-variance

Don't break SI-2066 (non-trans)