Add reserved username
Add reserved username

It's used like username on GHE when [domain is http(s)://[hostname]/gist](https://help.github.com/enterprise/2.4/user/articles/creating-gists/#creating-a-gist)

jamez14/octotree,duylam/octotree,Ephemera/octotree,jamez14/octotree,Ephemera/octotree,crashbell/octotree,buunguyen/octotree,crashbell/octotree,buunguyen/octotree,duylam/octotree