Pull with_machine_options context hash into the config for a machine.

Fixes #91
I believe you should be able to just use `new_resource.machine_options`.  Pulling current_machine_options this late in the game could give inconsistent results--for example:

```ruby
with_machine_options A
# The machine pulls A into "machine_options" as part of the resource constructor
machine 'blah'
# The provider runs after everything is finished, so it will pull B instead of A
with_machine_options B
```