support opening and closing quotes in --tests

[fommil]

Counter-inutitively, --tests="foo" does not work as expected, it must be --tests=foo (no ").

This always catches me out.

[szeiger]

All argument parsing is done by sbt and the test framework gets an array of Strings, similar to how a command line application gets its arguments from the shell. If you want to quote, it has to be around the entire argument, but with --tests there should never be a reason to do that.

[fommil]

it's more that one is used to passing regexes around inside "..." so it's easy to forget that it's not needed.