ioam/param: Version 1.7.0

Since the previous release (1.6.1), there should be no changes that affect existing code, only additions: A new param namespace object, which in future will allow subclasses of Parameterized to have much cleaner namespaces (#230). Started testing on python 3.7-dev (#223). param.version now provides functions to simplify dependants' setup.py/setup.cfg files (see https://github.com/pyviz/autover/pull/49). Although param should still work on python 3.3, we are no longer testing against it (unsupported by our test environment; #234). For more details, you can see a full list of changes since the previous release