Fix issue where uppercase style names weren't read in IE8

[bbodenmiller]

Converts all style strings to lowercase so that correct colorData hex value can be plugged in for named colors in IE8.

Previously the following would color nodes with a weird black color in IE8:

Node: {
            height: 60,
            width: 180,
            type: 'rectangle',
            color: 'LightCyan',
            overridable: true
        }

but this would work:

Node: {
            height: 60,
            width: 180,
            type: 'rectangle',
            color: 'lightcyan',
            overridable: true
        }