Removed slf4j-nop as a dependency in slick and jetty projects

"Embedded components such as libraries or frameworks should not declare a dependency on any SLF4J binding but only depend on slf4j-api. When a library declares a compile-time dependency on a SLF4J binding, it imposes that binding on the end-user, thus negating SLF4J's purpose."

http://www.slf4j.org/codes.html#multiple_bindings