unicode shortcuts documentation

this is in response to https://github.com/JuliaLang/julia/issues/7914

did i miss anything?

i think it would be nice to reiterate in the Functions section of the docs that unicode can be used for function names, but did not see a great place to do so.  any ideas?
It would also be good to mention that tab completion also supports super and subscripts e.g. ```\^1``` and ```\_1```