Bump yajl-ruby dependency from 1.1.0 -> 1.2.0

yajl-ruby 1.2.0 was recently released and contains a number of changes:

  https://github.com/brianmario/yajl-ruby/compare/eef5c48be81b6404af66da3f185ec9301e5214d8...fb61daad73340968badf6f84e41ec6931db2e87e