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?
This is not correct, it's aliased to `div` not to `/`:

```
julia> ÷
div (generic function with 25 methods)
```