promote isProduction to a global variable, https://github.com/phetsims/joist/issues/406
promote isProduction to a global variable, https://github.com/phetsims/joist/issues/406

Signed-off-by: Chris Malley <74b2712074b149d140079dbd7e875955d192e617@pixelzoom.com>

phetsims/chipper,phetsims/chipper,phetsims/chipper