Fix parsing of regex route within namespace

[abackstrom]

Modify parsing of regex routes within namespaces:

1. Prepend the namespace to all regexes
2. Interpret circumflex (^) anchor appropriately in relation to namespace
3. Ensure that negation only matches hits within the namespace

See #40 for original issue and test code.

Slightly wonky aspect of this: the prepending slash.

<?php

with( '/path', function(){
    respond( '@foo', $cb ); // matches /path/foo, /pathfoo, /pathfood, /path/hoofoot
    respond( '@^foo', $cb ); // matches /pathfoo, /pathfood
    respond( '@^/foo', $cb ); // matches /path/foo, /path/food
});

[chriso]

Thanks. The namespace functionality was a tad rushed.