Add support for thetaSketch

[jay kim]

ThetaSketch is nice feature. Please support thetaSketchs
@xvrl

[Xavier Léauté]

@jaynblue thank you, if you'd like to contribute support for it, we'd be happy to include it. Maybe the datasketches maintainers can chime in if they happen to plan any work around this. @himanshug ?

[Himanshu]

@jaynblue I don't think anyone is currently working on that. Please feel free to submit a patch.