jooby-apt: must add leading slash on path pattern

[surisuku]

The changes made to the mvc processing on 3.2.0 seem to have changed the path on some routes which didn't have an explicit '/' character on the specified path.

Taking the following code:

public class Test {
    @GET("test")
    public Object test() {}
}

This would produce a route for "/test" on version 3.1.4, but would produce "test" on 3.2.0.

From what I can see this change is not documented on the release notes for the version.