Updating readme (removing reference to LOG_LEVEL env var and documenting some new flags).
Updating readme (removing reference to LOG_LEVEL env var and documenting some new flags).

BrianGallew/cassandra_range_repair,ebuzzing/cassandra_range_repair,ebuzzing/cassandra_range_repair,gbagnoli/cassandra_range_repair,gbagnoli/cassandra_range_repair,BrianGallew/cassandra_range_repair