update install

Author: TomAugspurger

doc/source/install.rst

@@ -284,7 +284,7 @@ s3fs                      0.0.8              Amazon S3 access
 xarray                    0.8.2              pandas-like API for N-dimensional data
 xclip                                        Clipboard I/O on linux
 xlrd                      1.0.0              Excel reading
-xlwt                      2.4.0              Excel writing
+xlwt                      1.0.0              Excel writing
 xsel                                         Clipboard I/O on linux
 zlib                                         Compression for msgpack
 ========================= ================== =============================================================