ansible: node_exporter download behavior

[travisdowns]

The node exporter install ansible role downloads binaries locally and then uploads to all hosts. Imagine you are deploying something from your laptop over a dinky home connection to 100 hosts in the cloud. This is going to take a long time.

Can we add a mode where it downloads the binaries onto the hosts themselves? This could be as simple as using omit for the delegate_to: values in the tasks that deal with with the download and then skipping the upload ("propagate") step.