Fractional sizes

[edwh]

Is your feature request related to a problem? Please describe.
I want to be able to have sizes which are not just an integer.

Describe the solution you'd like
Something like the scale parameter in https://github.com/Justineo/vue-awesome.

Describe alternatives you've considered
At the moment it looks like the size parameter is used to include a class name. If you put a fractional value in there and then define your own class, then that works - but you get warnings about the custom validator on the prop failing.