Add vendor prefixes to user-select CSS
Add vendor prefixes to user-select CSS

Fixes 'user-select declaration dropped' warning on Firefox
According to http://stackoverflow.com/questions/8152526/css-3-0-user-select-property-replacement#8152641
"Note that user-select doesn't work in any browsers (that I'm aware of),
and only Gecko and WebKit support the vendor-prefixed equivalents:"

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