Eliminated dependency on Control.Monad

Parsing now pulls out the row needed so liftM2 from Control.Monad is gone.
I wrote a function "rep" which is replicateM in terms of mapM, the last dependency from Control.Monad is gone so I can remove that line.
With the import line gone I use a full line to define 2 help functions: rep and diff which gets the intersection of 2 lists (while expecting the arg to be a list containing 2 sub lists).
Writing diff enables removing the line that calculated the difference before.
Net gain: 1 line