Eclipse egit-github => jcabi-github

[cvrebert]

We're replacing egit-github with jcabi-github.

• egit-github
  • is somewhat abandoned
    • Its activity level is low
    • Code contributions don't tend to be reviewed promptly
    • It's using relatively outdated versions of some library dependencies
  • has extra Eclipse-related bureaucracy
  • Being usable outside of Eclipse doesn't seem to be much of a priority
• jcabi-github
  • responds fairly quickly to pull requests
  • is meant to be used as an independent library
  • has a decent (though incomplete) mocking feature to make unit tests possible

They're both somewhat incomplete with respect to all the current features of GitHub's API; such is life.