info for release 7.4.1

Author: Christian-B

README.md

@@ -9,5 +9,5 @@ See Also
 --------
  * [SpiNNaker online documentation](http://spinnakermanchester.github.io/)
  * [sPyNNakerGithub](/SpiNNakerManchester/sPyNNaker) for the implementation
- * [Combined python documentation](http://spinnakermanchester.readthedocs.io)
+ * [Combined python documentation](http://spinnakermanchester.readthedocs.io/en/7.4.1)
  * [PyNN documentation](http://neuralensemble.org/docs/PyNN)