Charges jump when keyboard nav is used

[KatieWoe]

Device
hp Laptop
OS
Win 7
Browser
IE
Problem Description
For phetsims/qa#221. Issue doesn't appear on all platforms. When keyboard nav is used to highlight one of the charge figures, that figure may jump to the side slightly.
Steps to Reproduce

1. Open the sim with internet explorer
2. Go to either screen
3. Use keyboard nav to move one of the figures back and forth
4. Change focus to the second figure (shift may or may not occur here) and move it back and forth.
5. Change focus back to original figure

Screenshot
https://drive.google.com/file/d/1P2hIV0E6J9TjowqtjYmlpzoVAkMyRKdk/view?usp=sharing

[jessegreenberg]

I observed this often while looking into #86 (only in Edge)

[jessegreenberg]

This is caused by the step size, which is 0.1 in this sim.

          this.setAccessibleAttribute( 'step', Math.pow( 10, -options.accessibleDecimalPlaces ) );

If I change accessibleDecimalPlaces in this sim to 3, the problem goes away. From phetsims/sun#413, I think we need to make this a required parameter or change how this is set.

[jessegreenberg]

If I use "any" as the value for the step attribute, this problem goes away, see phetsims/sun#413

[jessegreenberg]

@KatieWoe this should be fixed with phetsims/sun@31b65dd, can you please confirm?

[KatieWoe]

Seems to be fixed on master version of Coulomb's Law using Win 10 Internet explorer.

[jessegreenberg]

Thanks @KatieWoe, sounds good. Sun SHA phetsims/sun@31b65dd is the one we will need for the RC. @mbarlow12 if you run into any trouble pulling in the change please let me know.

[mbarlow12]

@jessegreenberg thanks—will do.

[KatieWoe]

1.0.0-rc.6 looks good on Win 10 IE