Make clear distinction of review_targets from targets in refactored code.
Ignore deleted characterizations before setting histone_mod_target/review_targets/organisms.
Docstrings are only at the top of functions/classes/modules, so convert to comments.
More concise inline if/else syntax
Switch order of if statement so we can 'bail out early' and avoid over-indentation
Bail out early
Bail out early
Move var setting into simplest scope; add comments for review.
Need to filter at top given my earlier refactoring of revs