invalid p-values on calculateDiffMeth call

[alexg9010]

BIMSBbioinfo/pigx_bsseq#42

[katwre]

The problem is that the Fisher test can generate p-values greater than 1 due to some numerical inaccuracies (according to Bren such values that are only above 1 by an amount that is less than machine precision) and the qvalue:qvalue function shows an error when it gets as input values greater than exactly 1. I opened an issue on github qvalue package about it (StoreyLab/qvalue#7).