small typos into docs and into the conf template

I changed the prefix into the key generation command from "/ndn/edu/memphis" to "/ndn/edu/colorado" just to be coherent with the rest of the tutorial, but I'm not sure that it could work, because in the template TOPOLOGY.MD, you've specified a different prefix "/ndn/edu/colostate" for router2.
Even if it's work, imho you should use just one prefix in both TOPOLOGY.md and SECURITY.md, because it could mislead/confuse users during the configuration.