Relax yajl-ruby dependency to let this play well

I'm currently unable to satisfy this dependencies:
```
Bundler could not find compatible versions for gem "yajl-ruby":
  In Gemfile:
    foodcritic (>= 3.0.3) ruby depends on
      yajl-ruby (~> 1.1.0) ruby

    yajl-ruby (1.2.0)
```