fixed FileRecordReader a bit.  now getKeyValuePairs takes an index
to a partition, a size (number of records) of the partition, and returns
an array of all key-value pairs (as strings) in that partition.  this
should be better for splitting off work.  might have set some offsets
incorrectly but how the fuck do i test PLEASE DONT BE MAD omg im going
insane i love everyone wait what hi nick