converge binaries used in integration tests and examples

[ryane]

Currently, any integration test (forthcoming in #355) or examples (elk, swarm) that use the Vagrant or Terraform provisioners are tied to the latest official release of converge. This means that they will break if they are updated to take advantage of new unreleased converge features. The only workaround at this point (afaik) is to upload a locally built converge binary to a public url somewhere and then build a custom version of the provisioner that points to that location.

It would be nice if we had a way for users and developers to run the tests and examples using a locally built converge.

Potential solutions:

• update Terraform and Vagrant provisioners to allow sourcing the converge binary from a location on the local filesystem
• publish nightly releases to a public location and support configuring the provisioners to point there
• Other ideas?