Parse arguments to :load the same way the shell does

[byorgey]

If you try to :load something from a path that has spaces, it stops prior to the space and claims it can't find the given module. One might even argue this is a bug since tab completion will fill in a file name with backslash-escaped spaces, but then :load chokes on it.

[byorgey]

Should really parse file names in the same way the shell does, since that's what tab autocomplete already does. i.e. with optional single or double quotes, escaped spaces, etc. And we can ALSO accept just plain spaces in the middle, since :load always has a single argument, so we don't need to worry about distinguishing where arguments begin and end.

[byorgey]

See https://hackage.haskell.org/package/ShellCheck-0.4.2/docs/src/ShellCheck-Parser.html for inspiration, e.g.

readSingleQuotedLiteral = do
    singleQuote
    strs <- many1 readSingleQuotedPart
    singleQuote
    return $ concat strs

readSingleQuotedPart =
    readSingleEscaped
    <|> many1 (noneOf "'\\\x2018\x2019")

Actually the ShellCheck parsing code is way overkill because it's also checking for various common issues, etc...