Added control to how dataset should be permuted through group argument
Added progress bar to parallelized permutation test
Changed parallelization interface to foreach and parallel
Corrected typos in vignette
When p-value is estimated to be zero by permutations, displays that it is inferior to one over number of permutations and not equal to zero
Corrected formula for estimating p-values ()
Added plots describing dataset and corrected typos in vignette
Removed buggy parallel interface (too many cross-platform problems)