Dependency requirements do not allow for integration with Phoenix v1.3.0-rc

[Garrett Dycus]

When running mix deps.get (Phoenix 1.3.0-rc.2):

Failed to use "phoenix" (version 1.3.0-rc.2) because
  terraform (version 1.0.0) requires >= 1.2.0 and < 2.0.0 *
  mix.lock specifies 1.3.0-rc.2

* This requirement does not match pre-releases. To match pre-releases include a pre-release in the requirement, such as: "~> 2.0-beta".

Perhaps change {:phoenix, ">= 1.2.0 and < 2.0.0"} to {:phoenix, ">= 1.2.0 and < 2.0.0 or ~> 1.3.0-rc"}

[lauren]

Thanks! Would you like to open a PR for it?