Fix typos

README.txt

 Introduction
 ============
 
-Marshals simple Python data types into a custom XML format.
-The Marshaller and Unmarshaller classes can be subclassed in order
-to implement marshalling into a different XML DTD.
+This module allows one to marshal simple Python data types into a
+custom XML format.  The Marshaller and Unmarshaller classes can be
+subclassed in order to implement marshalling into a different XML DTD.
 Original Authors are XML-SIG (xml-sig@python.org).
 
-Fully compatible with PyXML implementation, enable namespace support for
-XML Input/Output.
+Fully compatible with PyXML implementation, enables namespace support
+for XML Input/Output.
 
 Implemented with lxml