Provided Spark and assembly

Spark is now a provided deps, which allows easiest integration with other spark flavors if needed (→  wrapping project)

Assembly is configured but behaves weirdly → some resources cannot be loaded from jars, hours of explorations are suspecting
that folder in jar containing lots of entries exploses the netty resource loader...
Merge pull request #8 from andypetrella/spark-less-build

Provided Spark and assembly