Write to readonly property

[jylestrat]

Hi,

I've found a problem when using json-view with Safari 10.0 on iPad (IOS 10.3)
You can't write directly on style property in createNodeElement() method.
It cause an "Attempted to assign to readonly property" error

I've solved the problem by replacing following line :
lineEl.style = 'margin-left: ' + node.depth * 18 + 'px;';
by
lineEl.setAttribute("style", 'margin-left: ' + node.depth * 18 + 'px;');

It work fine now on Opera.