futher refactoring
futher refactoring

The script produces 99.85% identical output to initial version. The differences
in 7208 de novo events are:
 - 4 sites appear in one de novo input, but not another
 - 4 sites have slight differences in P values, nudging them above the filtering
   thresholds.
These differences have negligible impact on the filtered output.

jeremymcrae/denovoFilter