Revert "Merge pull request #2 from sferik/alt-split-delimiter"

This reverts commit 8f2a550480708d65f263ccaaea602f9bb62850df, reversing
changes made to 10a338d560679c0b7bfe35f738f504954b616982.
Add Rake task for benchmarking
Fix specs to print expected/given correctly

Also ensure that the command doesn't modify its arguments
Modify to support longer delimiters without slowing it down too much