Spinner uses step of 0 when step is 1e-7 or less

[pmize3]

The spinner's _precisionOf function fails to properly return the decimal places when the step is smaller than 1e-6. This is due to the fact that the number is represented in the "XeY" instead of the "0.000" format when the number is smaller than 1e-6 and the _precisionOf function is expecting the latter.

Example: var spinner = $( "#spinner" ).spinner({step: 0.0000001});

​https://jsfiddle.net/161h6821/