Add Environment support

[ChrisMcKenzie]

Github API can optionally send a deployment environment it would be nice to be able to define a different set of servers for each environment.

maybe something like this:

servers:
  development:
    provider: list
    options:
      list:
          -
            address: 127.0.0.1

@ericgreene || @krisbarrett || @mattwarren1234 do you have any input?