Issue-818. RtGithub.java constants visibility modifiers reverted.
Issue-818. RtGithub.java constants visibility modifiers reverted.

pecko/jcabi-github,shelan/jcabi-github,prondzyn/jcabi-github,zygm0nt/jcabi-github,YamStranger/jcabi-github,cezarykluczynski/jcabi-github,cvrebert/typed-github