Trying to get group pages working.
Found problem: group_trad_to_lin(traditional_group) is interpreting all traditional_group as strings (which means they're all treated like f groups).
Solution: need to check whether traditional_group really is a string.
Ideas how:
1) See if traditional_group responds to .to_i (if yes, is a main block group; if not, is an f block group)
2) Use regular expression?