changed default sprite size to 32 to work better with large datasets

[contractorwolf]

I changed the default sprite size to 32 to fix issues that I was having facets crash when trying to display a dataset with 33 columns and 90k records. It was suggested by @jimbojw to set the sprite to 32 pixels, so here is the PR for that. The Issue (reported by me) is located here: https://github.com/PAIR-code/facets/issues/115#issuecomment-378941849

I tested the suggest change on my dataset (no longer crashes) and tested just this change locally on the default dataset in facets. Let me know if there is anything else I need to do.

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[contractorwolf]

I signed it!

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[jimbojw]

Thanks for sending us a PR. Unfortunately, the smaller the sprite size, the fewer pixels are available for rendering text, causing it to appear pixelated. I'm concerned that this would make smaller data sets look worse. Is there any way we could dynamically compute a good default based on the data set size?

[contractorwolf]

@jimbojw yeah I can do that, I just worry about adding the additional complexity to a code sample. This is the first time I really used this but for mine I was just using "credit score" to fill the display which is only 3 digits and looks fine at 32px, but i don't know what kind of items other people would be filling each dot with. Can you give me some examples that you are using on the "display" so I can imagine it better? Ill adjust this PR, what would you suggest the breakpoint should be when switching between 64 and 32px? 50k records?

[contractorwolf]

@jimbojw I made a new PR integrating your concerns and making it dynamic: https://github.com/PAIR-code/facets/pull/119

[contractorwolf]

let me know if that doesnt work