Flowz

* Python 3 compatibility fixes

* `flowz.util.channel_inner_join` takes any number of channels.

* Adds introspection tools for channel management objects:
* `get_channelmethods`
* `get_channelproperties`
* Changes logger names for artifacts and downgrades some messages from INFO level to DEBUG
* This change in logger names could break deployed logging configurations, and for this
reason, we incremented the minor version; otherwise this would be a micro bump.

* Adds the `channelmethod` decorator as a callable-oriented version of `channelproperty` (Issue 41)
* Includes ipython notebook user guide (thanks to Patrick Rusk!)
* Suppresses the "future exception not handled" warnings from tornado for channels. (Issue 30)

* Adds the new `flowz.channels.tools` module for utility functions/helpers
that extend the flexibility of channels without expanding the core interface.
* Adds rolling window functionality therein.

* Removes (silently) deprecated targets classes and tests
* Including support within the `flowz.app.Flo` class
* Downgrades some logging messages to DEBUG level
* Changes some keyword parameters on windowby/groupby (from keyfunc on both
to keys_func and key_func, respectively).