Added --clobberlevel option.
 * set clobberlevel 2 to overwrite an existing epochs.txt file and update
   with new flt files
updates for handling sub-arrays and now assumes onimage=True
  * now catching an exception triggered by WCS for subarray images
  * assume onimage=True, pending WCS checks, so that WCS errors don't mistakenly exclude good data
Updates to WFC3 UVIS CTE correction
 *  grabbed new fortran code from stsci on 2014.12.03
 * User must recompile their own executablesgit status!