Better defaults in REPL

[pfitzseb]

Should either automatically open a new tab in the default browser (might require a dependency on Mux or a HTTP.jl based server implementation, like what Juno does).

[pdeffebach]

this would be wonderful. Blink windows open up pretty quickly so it gets by. having a browser tab open by default would be the first-best option imo.

[pdeffebach]

I would also add that maybe the cell-size is too big when using Blink. I know it can be given as an input to the function, but a smaller default would be nice.