read_sas column limit
I get an index error for reading any sas file (sas7bdat) over 2047 columns wide.  This issue can be reproduced simply by generating a 2048 column width file in excel, importing into SAS and writing it back out as sas7bdat file then trying to read with read_sas.

[testdata.zip](https://github.com/pandas-dev/pandas/files/2788506/testdata.zip)

IndexError: index 1 is out of bounds for axis 0 with size 1
