Publish v1.9.0

[davidarnold]

Per HISTORY.md, v1.9.0 was released on Aug 20, 2016. However, there is no existing tag for 1.9 and gem is current installing 1.8.

Please publish the 1.9 gem. In my personal use case, I would like to make use of the new recursive_to_h method for JSON serialization.

Thanks!

[ms-ati]

@tcrayford If it's helpful to you, my offer still stands to take over maintenance of this gem (which my team still uses every day). Please feel free to hand it off when you are ready, I realize that you no longer have the time even to respond to these issue requests.