Update README.md

Author: leongor

README.md

@@ -1,5 +1,6 @@
 streamsx.regex
 ==============
-This toolkit provides support for [RE2](https://code.google.com/p/re2) regular expression library. 
-Web page with SPLDoc for operators and samples: [streamsx.regex SPLDoc](http://ibmstreams.github.io/streamsx.regex).
+This toolkit provides support for [RE2](https://code.google.com/p/re2) regular expression library.
+
+RE2 uses automata theory to guarantee that regular expression searches run in time linear in the size of the input. Web page with SPLDoc for operators and samples: [streamsx.regex SPLDoc](http://ibmstreams.github.io/streamsx.regex).