added xticklabel_rotate.m

this function is SUPER helpful for graphing anything involving GH
profiles, since the names of those bacteria can be mighty long and
overlap unless rotated
uploaded statsCategorical

function-in-the-making; generates a matrix of abundancies of the
bacteria found in the samples that have viable data for the column
specified.

will put more comments explaining how things work later; just wanted to
push this out in case others wanted to use