added license file

LICENSE

+This software was developed at the United States Naval Academy (USNA)
+by employees of the Federal Government in the course of their official
+duties. Pursuant to title 17 Section 105 of the United States Code
+this software is not subject to copyright protection and is in the
+public domain. It is an experimental system. USNA assumes no
+responsibility whatsoever for its use by other parties, and makes no
+guarantees, expressed or implied, about its quality, reliability, or
+any other characteristic. We would appreciate acknowledgement if the
+software is used. This software can be redistributed and/or modified
+freely provided that any derivative works bear some notice that they
+are derived from it, and any modified versions bear some notice that
+they have been modified.