Fix Market.getElementRect function.

The current coffee code compiles to the following javascript code:

        if (computedStyle.getPropertyValue('float' !== 'none' || computedStyle.getPropertyValue('position' === 'absolute'))) {
          if (childRect = getElementRect(childElement)) {
            childRect;
          }
        }
        return void 0;

That is obviously not the expected behavior.
Merge pull request #96 from LordJZ/develop-getelementrect

Fix Market.getElementRect function.