Update README.md

Rectifying a typo

Author: ederrf

README.md

@@ -15,7 +15,7 @@ lists, maps, and unions.
 
 ## ORC File Library
 
-This project includes both a Java library and a C++ library for reading and writing the _Optimized Row Columnar_ (ORC) file format. The C++ and Java libraries are completely independent of each other and will each read all versions of ORC files. But the C++ library only writes the original (Hive 0.11) version of ORC files, and will be extened in the future.
+This project includes both a Java library and a C++ library for reading and writing the _Optimized Row Columnar_ (ORC) file format. The C++ and Java libraries are completely independent of each other and will each read all versions of ORC files. But the C++ library only writes the original (Hive 0.11) version of ORC files, and will be extended in the future.
 
 Releases:
 * Latest: <a href="http://orc.apache.org/releases">Apache ORC releases</a>