class-based method of calculating stats to facilitate calculating more than one at once
added perm function for all stats
added permutation functions and fixed some typos
added more documentation. reduced number of perms in examples
added Z scores
fewer compilation units
consitent variable names now
Li and Leal collapse stat added
added Li and Leal collapse stat to all permutations.
updated roxygen
Merge branches 'dev' and 'master'