elseif statement

[maxfl]

I wonder why fish doesn't have 'elseif' statement.
I think it is very useful thing. Event in case of one nested if statement, it saves one identation level and makes it easier to follow closing 'end's.

[ridiculousfish]

I first implemented this as a new builtin, "elseif," but then decided I didn't like that. All fish builtins are real words. So now it's "else if":

if false
    echo "Branch 1"
else if true
    echo "Branch 2"
else
    echo "Branch 3
end

Docs updated too.

To git@github.com:fish-shell/fish-shell.git
ff12446..1a59346 master -> master

[maxfl]

That's cool. Thank you.