Make many scripts in src/utils Python 3 compatible.
don't resample ptable xs if diff temperature but same E
set last prn of a nuclide whenever a prn is needed
Merge remote-tracking branch 'mitcrpgopenmc/develop' into ptable-resample
Merge remote-tracking branch 'mit-crpg/openmc/develop' into ptable-resample
Added zero-padded statepoint names
Wrapped batch number zero padding into a function
Added zero padded filenames for source files

Also correcteted statepoint filenames in write_source_point
Updated tests for zero padded filenames
Commented zero_padded_batch
Merge branch 'develop' into zero_padded_statepoint
Moved zero-padding features to string.F90
Fix distance-to-surface calculationg for general plane surface.
account for differences in band probabilities at different energies
Fixed zero_padded error message typo
Change quick install instructions to be more explicit about checking out branch
master.
Merge remote-tracking branch 'mit-crpg/openmc/develop' into ptable-resample
Merge remote-tracking branch 'openmc/ptable-resample' into ptable-resample
Fixed overflow error in count_digits
fixed comment that was over 80 characters