Add book and mailing list to list of ruby books

Changes:
- Add book Learn to Program by Chris Pine
- Add ruby talk mailing list which talks about general topics about Ruby
  and is the most popular mailing list according to:
https://www.ruby-lang.org/en/community/mailing-lists/
Merge pull request #12 from jonathanyeong/master

Add book and mailing list to list of ruby resources