Move unit test files

Mirror the source code file structure in the unit test organization.
Merge pull request #535 from jugglinmike/move-tests

Move unit test files
Clone input nodes when inserting over a set

This patch increases parity with jQuery, specifically in cases where
manipulation methods are called with existing nodes on sets containing
more than one element. In such cases, the provided node should be cloned
prior to insertion (excepting the final element in the set, where the
original node should be inserted).