Pass options through to the HTML2HAML gem with the json api

[itsthatguy]

• Adds ability to pass options through to HTML2HAML with the json api
• Adds new test for the new options feature
• Adds ruby version to Gemfile to fix heroku deploy crash

[itsthatguy]

Ultimately I want to use this in the sublime html2haml package.

https://github.com/itsthatguy/sublime-html-to-haml/commit/9454708a7011cf53b58c751b074c69f63f1c77f0