Test foldRight, foldLeft of product.

Conflicts:
	tests/src/test/scala/scalaz/FoldableTest.scala
Fix repeated _2-injection in product foldLeft, foldRight.
_1 was ignored in product fold*1s, except foldMap1.
Tests for fold*1s on product.

Conflicts:
	tests/src/test/scala/scalaz/Foldable1Test.scala
Bad cherry.
Merge pull request #431 from S11001001/topic/product-fold-bugs-71

Fix product folds