DataFrame repr regression
There's a call to `to_string` in `DataFrame._repr_fits_horizontal` that is **drastically** slowing down `repr`ing of large `DataFrame`s and incidentally makes the option `max_info_rows` useless since that call occurs before `max_info_rows` comes into play. 

Is there any way to compute the length of the column `repr` without using the entire frame as a string? Also, for large frames that will create tons of temporary strings that could cause a segfault if one doesn't have swap enabled (that's probably a bit alarmist; I'm trying to be thorough here. :)) At best it will raise a `MemoryError` exception. 

What's the thinking here? One could check `max_info_rows` in `DataFrame._repr_fits_horizontal`, but that's more of a stopgap solution than an actual one. Using `cStringIO` is not a viable solution: it only gives a ~29 ms speedup. Also, should there be a vbench for `repr`ing?
