Re: [css-flexbox] Renaming flex-basis:auto for less confusion

I'm also for number 2. Having used flexbox for a while now I'm fairly 
used to the idea that auto means size look-up when dealing with flexbox. 
`content` may not be too intuitive but there are already a number of 
not-too-intuitive keywords in the flexbox spec, so I'd rather have 
another one than break backwards compat.