Default resource requirements

[adamstruck]

A Funnel worker needs some minimum amount of resources to run.

If a task message is submitted that doesn't include resources Funnel should pick some reasonable defaults.

[buchanae]

There are cases where you're saying "this task is lightweight and takes up almost no resources". In that case, I think the required cpu/ram is zero. Not saying that's the default case, but I'd like to make sure it's allowed/possible.