drop ruby 1.9.2, add latest stable
drop ruby 1.9.2, add latest stable

Ruby 1.9.2 is EOL, and 1.9.3 is not far behind. Foodcritic 4.x requires
at least 1.9.3. This currently blocks travis tests from completing on 1.9.2

Ref: https://github.com/acrmp/foodcritic/commit/9c312ca2113dfd0185f0dbcd3e7d9a6a32d0bf99

Nordstrom/guard-foodcritic