Consider removing multi_json dependency

[yob]

Hi,

JSON has been part of the ruby stdlib since 1.9.0 (see ruby/ruby@af1c4167), and the latest version of poltegeist requires ruby 1.9.3 or better.

Would you consider removing multi_json as a dependency, and just using require 'json' instead? Rails recently made a similar change (rails/rails#23453), which has prompted other libraries to consider the same issue (like simplecov and stripe).

See also this recent blog post.

Thanks for a great library!

[route]

Sounds good! Mind opening a PR?

[yob]

Sure, I've opened #734

[route]

Thank you!