Streaming node add

[FinchPowers]

Rather than waiting for all spot instances and then for all instances ssh to be up prior to starting adding the nodes to a cluster, adds the node as they come ready.

• May be useful when adding many nodes at once. The greater the amount of added nodes is, the greater the probability this will be beneficial is.
• No difference when adding a single node.

Note: This is based on 2 bug fixes pull requests, namely #433 and #433

[cancan101]

Why did you close this PR?

[FinchPowers]

I was just cleaning my repo and forgot about that PR.
I should make a new one with all the updates I made to my version.