Python 3 Compatibility

[Adamtaranto]

Lines 250 and 285 in histogram.py cause the Python3 print function to bug out when trying to parse the default "options.dot" character, "∎".

Throwing an error like this:

Traceback (most recent call last):

File "/user/bin/Filtlong/scripts/histogram.py", line 325, in options.agg_key_value), options)

File "/user/bin/Filtlong/scripts/histogram.py", line 250, in histogram print("Each " + options.dot + " represents %s bases" % bucket_scale_str)

UnicodeEncodeError: 'latin-1' codec can't encode character '\u220e' in position 5: ordinal not in range(256)

I haven't been able to figure out how to get the block to render with py3 but replacing the default dot character with '*' seems to do the job.