add sbt-dependency-graph to project build
remove junit runner from tests
initial commit of TileIdPartitioner - a partitioning scheme for HDFS-based RDDs of tiles
fix TmsTiling methods to work on the correct type (Double or Long)
add height/width to TileBounds
initial commit of SaveImageFunctions - the ability to save an RDD of tiles to HDFS
initial commit of GeotrellisSparkUtils
minor fixes to LoadImageRDD