Changed computedStyle return string, now it works in Firefox

[mdesplenter]

This fixes issue #2

[pomber]

Thanks @mdesplenter. Two things:

1. Given that getStyle function receives "font" as a parameter we should probably add this hack outside this function. Maybe in a getFontStyle function.
2. The font shorthand that was previously being used includes more than just font-size and font-family. It includes font-style, font-variant, font-weight, font-size, line-height and font-family. The fix should include all those styles following the font shorthand format.

[pomber]

Here is a jsbin I was using some time ago to test getComputedStyle in various browsers: https://jsbin.com/yoholarina/1/edit?html,console
Maybe it can help you.