Added note about spark-prepare.
Added note about spark-prepare.

CompilerWorks/spliceengine,CompilerWorks/spliceengine,splicemachine/spliceengine,CompilerWorks/spliceengine,CompilerWorks/spliceengine,splicemachine/spliceengine,splicemachine/spliceengine,splicemachine/spliceengine,CompilerWorks/spliceengine,splicemachine/spliceengine,CompilerWorks/spliceengine,splicemachine/spliceengine,splicemachine/spliceengine