Add tests

+ Add ``mocha``, ``should``, and ``irc`` as dependencies
+ (add ``package.json``)
+ Add test suite to ``package.json``
+ Add ``module.exports`` to ``psend.js``
+ Add IRC test suite
- Remove test from main ``psend.js``
+ Add ``mocha.opts`` with sensible defaults

The test failed; it may be desirable to ensure that the test is supposed to fail before merging this pull request.
It may also be desirable, and presumably best practice, to integrate a CI platform such as Travis once this framework is in place.

To test, use ``npm test``.

The test uses the external ``irc`` module to make it more of a controlled test.