resolve #149 - multi_param() method

allows you to call param() in list context without a warning being
raised by the module. update documentation to make it clear that
this method is an addition and back compatibility remains although
a warning *will* be raised if param() is called in list context from
user code

bump version and update Changes to explain that all existing issues
have been cleared so testing of the module is advised before an
upgrade to version 4.00 and above