Fixing: https://github.com/weavejester/lein-ring/issues/46

Added: leiningen.ring.src-paths

Searches project for source-paths.

This only searches the immediate project checkouts dir,
the same as leiningen uses for it's classpath.

Changed: leiningen.ring.server

src-paths are passed to ring.server.leiningen/serve in options.
These are always provided. It is slightly problematic to determine whether
they are needed as ring-server determines from LEIN_NO_DEV env
variable whether to use reloading or not.

Preemptively updated ring-server add-if-missing to ring-server 0.2.6