Add Humble Play

[carloslbello]

Humble Play is the backend for Humble Bundle's in-browser asm.js games and includes a cloud save service.

I have a working version of a module that directly calls Humble's cloud API, but this is undesirable as 1) it requires the user to supply a session ID token which must be extracted from the browser and 2) it requires network access when accessing files (whereas iCloud and Steam Cloud have local copies of files).

If Humble decide to make a native (C) implementation of their cloud service, I will pursue creating a module which uses that instead.

Addition of Humble Player would possibly allow the addition of sync functionality for these games: Democracy 3, Dustforce DX, Super Hexagon, and Zen Bound 2.