Fixed mixed version and upgrade test for older riak's.

The tests were not meant to handle an upgrade from non-1.3 versions of
riak; there were designed to ensure an upgrade from early 1.3 would go
smoothly. Thus, the checks (and skippings w/o error) if the previous
version of riak is too old for the test to be valid.
Added wrapper fun running some tests individually.

This is to make it easier to test specific changes to them.
Documented the config option added.
Merge pull request #326 from basho/mw-fix-cascading-repl-for-early-versions

Fixed mixed version and upgrade test for older riak's.