README should discuss branching situation

[SethTisue]

there's a 1.0.x branch and a master branch. at one time I knew how they were different, but now I've forgotten. could this be covered in the readme...?

in particular, I'm wondering which one we should be tracking in the Scala community build. (currently we are tracking master.)

[sjrd]

Is 1.0.x even still relevant?

[SethTisue]

note that 1.0.x is currently the default branch here on GitHub

[SethTisue]

@gourlaysama this might be an easy one for you to address and close out...?

[SethTisue]

1.1.x is the default branch now

[SethTisue]

the master branch no longer exists, and the community build tracks 1.1.x now