Adding basic support for specifying create timeout.

[hozn]

For me the Vagrant VMs were never building before apparently being timed out by terraform. My golang knowledge is rudimentary, to say the least, but I examined how this was implemented for another provider and got a version that appears to work (respecting the configured timeout values).

Happy to update the docs too, if you're amenable to this PR.

[bmatcuk]

Hey @hozn, thanks for the PR! Do you know if the timeouts are coming from terraform, or from vagrant? According to the terraform docs the default timeout should have been 20 minutes whereas I see you defaulted to 2 minutes in your PR. Are you using the timeouts {} directive in your terraform configuration?

[hozn]

Hmm ... I am using that directive and it seemed to address an issue, but it sounds like I need to investigate further what might have been timing out and whether that was a coincidence!

[bmatcuk]

Hmm, ya, I'd like to get to the bottom of the problem to make sure we've got the right solution =)