meanMenuOpen <span> should not be self closing

[m-vdv]

meanMenu uses the following default code to create a "hamburger" menu icon:

meanMenuOpen: "<span /><span /><span />"

However <span> is not a a self-closing tag, this should be changed into:
meanMenuOpen: "<span></span><span></span><span></span>"

Otherwise browser compatibility isn't at its best and it might turn out like this:
<span><span><span></span></span></span> (nested spans)

[prgriffithsdev]

Solved my issue! +1 for this :)