Support Google Tasks

[wizonesolutions]

Word on the street says that Any.do can synchronize with Google Tasks. I use Any.do, and I rather like it. I also need a good alternative task manager for when I develop my Big Idea, so this is in my interest. I would want those tasks to get synced with HabitRPG also.

Punch list for this:

1. Investigate if Any.do really syncs with GTasks.
2. Test it manually; what happens when I check off a GTask task? Does Any.do pick it up? Add and delete also.
3. If all checks out, we continue. If not, might do it anyway. GTasks has a decent Android app, and I could live with it.
4. Implement the standard functionality that RTM already has — add new, delete deleted, complete on GTasks when completed in Habit. Use the hts_gtasks key for custom metadata. hts_external_id and hts_external_source should reflect GTasks also. I didn't put them in there for nothing.
5. Add logic to add a note saying where the task came from, or maybe prefix the task with the service abbreviation. This is because I might import some of my RTM tasks to GTasks, and I want to be able to distinguish them at a glance.

If you beat me to this, send me a pull request! Any.do is popular right? :)