Eliminate mrt-ingest-ruby, move code to mrt-atom

[terrywbrady]

• The only client of mrt-ingest-ruby is mrt-atom
  • confirm this with Mark
• Migrate logic into the mrt-atom code base
• Deprecate mrt-ingest-ruby from rubygems

[elopatin-uc3]

@elopatin-uc3 contacted UCB LIT to ask if this is in use.

[elopatin-uc3]

Confirmed not in use.