Made single-argument _and(boolean) method public, for other boolean conditions.

The idea is that it's easier to see the call to `super.equals(obj)` and
therefore more explicit that you're including the superclass's
implementation. Of course, it's still possible to call
`super.equals(obj)` directly and `&&` it with the result of
`eq.equals()`.
Added a compareStrictly() static factory method for checking class equality.

Some people feel strongly that `equals(Object)` should only return
`true` if the two objects are instances of the same exact class. This
new method gives an easy way to do that.
Added note about development status to main README.
Added computeForLargeSet() static factory method.

HashCode now includes two very different hashing algorithms. The caller
selects the algorithm by the static factory method they call.
Merge branch 'iss3'