Shade some repl dependencies to mitigate the building difference between Spark1 and 2

Some dependencies are different between Spark 1 and Spark 2, like json4s, py4j, it makes Livy hard to support multiple versions simultaneously, especially Json4s dependency, so here propose to shade these dependencies to mitigate the difference. For json4s, the final goal is to remove the dependency, which will be addressed in LIVY-118.