Sudo-less user install

[BrenekH]

Requiring sudo for a user install isn't best practice for security and flexibility reasons.

The current reason that sudo is required (as far as I can tell) is for the installation of the Bash completions. If a flag were introduced that controlled whether or not the completions were installed (either --no-completions or --completions, depending on the default behavior), that would allow a user to choose whether or not to install with sudo.

Obviously, the perfect solution here would be to put the completions in a user directory, but I am unsure if Bash has this ability.