Added a simple heatmap based on retentionHeatmap that can be used for any 2-label data

[loufranco]

I based this visualization on the retention heat map, but simplified it so I could use it on my more generic 2-label data.

I don't know what you use to minimize, but I could add a commit with the correct minimizations if you tell me how to do it.

[loufranco]

@leqilong What is the best way to move this PR forward? I can add the min.js if you tell me how -- I could make any other changes you want.

I'm using this now in a mode report and it would be nice if I could just include it (which requires it to be hosted by mode)

[leqilong]

Hi @loufranco, sorry for missing your PR. We use uglifyjs to minimize the alamode.js file. You can use this command to do so:
uglifyjs --compress --mangle -- alamode.js

As for the alamode.css file, we use csso. And the command is:
csso alamode.css --output alamode.min.css

[loufranco]

Ok @leqilong, I minified. Let me know if there's anything else I need to do.

[leqilong]

@loufranco Thanks. I've deployed your changes. You should be able to start using it now.