Update README.md

Author: scheinerman

README.md

@@ -8,7 +8,7 @@ appended.
 The functions in this module work for all types of `Integer`, `Rational`, and `Mod`
 entries in matrices. Other exact numbers may work as well, but are not tested. 
 
-As the goal of this module is always to give exact answers but, at the same time,
+As the goal of this module is always to give exact answers and, at the same time,
 be type stable, the results of many of these functions are `big`. That is, the `detx`
 of an integer matrix has entries of type `BigInt`.