Bump github-api dependency to 1.40

Newer versions of github-api change the way you call connectUsingOAuth
to take the full API url. E.g. "https://api.github.com" or
"https://github.enterprise.com/api/v3"
Add an explicit API URI field to GithubSecurityRealm
Merge pull request #11 from bjeanes/master

Working GitHub Enterprise support