Updated instructions to reflect changes.

[DavidGinzberg]

Updated the instructions to reflect UI changes on Codio and more accurately represent the setup process including edge cases caused by previously signed in accounts or shared computers (with previously signed-in accounts).

[moollaza]

@DavidGinzberg thanks a lot for contributing and helping to keep the docs up to date! We really apprecaite it :smiley:

@talsraviv any thoughts on this?

[talsraviv]

:+1: LGTM