Update README.md

Author: firefly-cpp

README.md

@@ -50,6 +50,10 @@ Jozef Stefan Institute, Ljubljana, Slovenia, 2012
 
 I. Fister, I. Fister Jr.,  X.-S. Yang, J. Brest. [A comprehensive review of firefly algorithms](http://www.iztok-jr-fister.eu/static/publications/23.pdf). Swarm and Evolutionary Computation 13 (2013): 34-46.
 
+## License
+
+This package is distributed under the MIT License. This license can be found online at <http://www.opensource.org/licenses/MIT>.
+
 ## Disclaimer
 
 This framework is provided as-is, and there are no guarantees that it fits your purposes or that it is bug-free. Use it at your own risk!