Improve docs about leading and trailing slashes
Document behaviour of StrictSlash and PathPrefix better, and add tests to nail this down
Convert TestStrictSlash to a table driven test
Add tests for all four StrictSlash cases
Propagate StrictSlash to subrouters instead of rudely turning it off
Merge pull request #51 from ttencate/master

Make PathPrefix more polite towards StrictSlash setting, and add better tests for the latter