added sentence to library index

ba809979 · James Bergstra · e7b8f859 · ba809979
--- a/doc/library/index.txt
+++ b/doc/library/index.txt
@@ -5,7 +5,8 @@
 Library Documentation
 =====================
-This documentation covers Theano module-wise.
+This documentation covers Theano module-wise.  This is suited to finding the
+Types and Ops that you can use to build and compile expression graphs.
 .. toctree::
   :maxdepth: 1