change capitalization in README file to make acronym apparent

README

-Python Open Source Waveform ExtractoR: An open source, python package to monitor and post-process numerical relativity simulations
+Python Open-source Waveform ExtractoR: An open source, python package to monitor and post-process numerical relativity simulations
 Author(s)    : Daniel Johnson <dsjohns2@illinois.edu>
                E. A. Huerta <elihu@illinois.edu>
                Roland Haas <rhaas@ncsa.illinois.edu>