ENH: raise a more a useful exception on empty files
@jreback any last words before i merge this? the fix is that the heuristic for table sizes assumes that there are columns and then if there aren't it will divide by zero so i catch and give a valueerror with a more useful msg.
 this seems very specific
what does it do now wih your example?
 raise a valueerror telling the user that they've given a file with no columns
 better to catch a more specific exception than to hide a bug in the parser with `except:` no?
 why is that bad? seems clear to me
 why is this a bug if it raises a reasonable exception?
 no i added that
 it raises zerodivisionerror before this 
 the fact that there's a heuristic in `parser.pyx` that could possibly divide by zero is not something a user should have to deal with...right?
 sorry by now you mean before this pr i thought u meant after it
 oh i c

can this be caught lower down (eg detected in tr parser)
 sure should i do that
 there's another possible issue here that i hvaen't tried let me check it out
 iirc this is easiky detectable in parser.pyx
(you can raise the same error that u out here)
but it only catches in this circumstance so it's narrower (and if something else is hiding will see that separately)
 @jreback i think this is ready 2 go if u think so
 looks good
