Can't pass rr-opts

[NickHu]

No matter what I try to do, I can't pass options to rr. For example:

❯ cargo rr replay mytrace -s 1234 
error: Found argument '-s' which wasn't expected, or isn't valid in this context

USAGE:
    cargo rr replay [trace] [rr-opts] [-- <gdb-opts>...]

For more information try --help

[NickHu]

So the problem is essentially that any rr option you would want to use begins with -, which then gets intercepted by clap rather than passed through.

[dzfranklin]

Fixed in #14