WIP - Rolling back Waitlist to simpler implementation.
WIP - Rolling back Waitlist to simpler implementation.

- Invalidating the computation you're in the middle of causes an infinite loop
  that I thought I had stopped but couldn't quite figure it out.
- Rolling back so that it works with a simpler approach. Each ready handle will
  invalidate the computation when its state changes, vs. trying to aggregate
  them for now.
- Will revisit once tests are updated.

Sombressoul/iron-router,Aaron1992/iron-router,sean-stanley/iron-router,Hyparman/iron-router,sean-stanley/iron-router,Hyparman/iron-router,iron-meteor/iron-router,abhiaiyer91/iron-router,leoetlino/iron-router,tianzhihen/iron-router,firdausramlan/iron-router,Aaron1992/iron-router,DanielDornhardt/iron-router-2,assets1975/iron-router,TechplexEngineer/iron-router,assets1975/iron-router,ecuanaso/iron-router,DanielDornhardt/iron-router-2,jg3526/iron-router,iron-meteor/iron-router,snamoah/iron-router,TechplexEngineer/iron-router,tianzhihen/iron-router,abhiaiyer91/iron-router,snamoah/iron-router,appoets/iron-router,firdausramlan/iron-router,Sombressoul/iron-router,appoets/iron-router,ecuanaso/iron-router,jg3526/iron-router