Improve tab completion
Improve tab completion

Usernames with spaces can now be completed.

Special characters in front of the username will now be preserved.
This requires usernames to start with an alphanumeric character,
which fortunately we already enforce.

sirDonovan/Pokemon-Showdown-Client,panpawn/Gold-Client,asgdf/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,panpawn/Gold-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,panpawn/Gold-Client,submindraikou/Pokemon-Showdown-Client