Use this R function to process read count files created by either the perl code
of Venkat Seshan (type vpl) or Nick Socci's two counters. Type "ns1" has 22
columns which are ACGT counts on positive and negative strands while "ns2" has
just 8. The former counts the reads where as the latter the fragments
(overlapping read pairs are not counted twice). This function can be made
available using:

   source(system.file("extRfns", "readSnpMatrixMSK.R", package="facets"))
