Add a new feature type to test extensibility

[MichaelCurrie]

Currently the WormFeatures class holds information about four feature types: Posture, Morphology, Locomotion, and Path. Each of these types has its own class.

As an exercise to show the extensibility of this framework, please create a new feature type, with its class definition in its own module, and add it to the WormFeatures class.

[MichaelCurrie]

This might be something that Semon Rezchikov, an undergrad affiliated with Adam Marblestone, might be interested in working on.

[JimHokanson]

@MichaelCurrie It would be nice to have something a bit more specific than that. Adding motifs ala Andre from MRC might be a better task.

[MichaelCurrie]

Great point Jim. Here's a link to André's paper on that.

[MichaelCurrie]

This is covered by #117