round value with decimal precision

[fl4p]

jsbin with paper-slider: https://jsbin.com/votacuzaxe/edit?html,output

The current work around seems no to be working anymore (compiler optimizations?).

My fix rounds the value with decimal precision.

[fl4p]

Just fixed a rounding issue that made the tests fail.

And:
Checking for step < 1 is not sufficient, precision issues can occur for all non-integer steps, like 1.001. I found the only solution is to compute the decimal places of step with its string representation and use this precision for final rounding of value.

[tapionx]

i confirm the issue, please merge this PR