Include "precision" setting from Calca

[Zettt]

I've used Calca many times before. Because I work with cryptocurrencies a lot, I loved its ability to calculate precise numbers, up to 8 digits. The setting was pretty simple: @precision = 8, somewhere at the top, and it would change for the text. Would love to see this feature here, since Calca is definitely dead.

[spoike]

Will have to investigate this.

Seems like javascript Number has a toPrecision method so it seems possible to print out numbers at a given precision.

Not sure about floating point precision per se, though that might be a non-issue.