Libcloud 469 add reserved instance support

[cderamus]

No description provided.

[Kami]

You can drop the Ex prefix. I know one class in EC2 driver uses it, but that's mostly an artifact from the past.

Nowadays we only use ex prefix for methods and arguments.

[Kami]

This class could potentially inherit from Node and you can then just pass None for public_ips and private_ips argument, right?

Adding docstrings for attributes which are not already present on the Node class would also be good (just by looking at the constructor, I don't know what the type attribute represents).

[cderamus]

I went ahead and made the requested changes. To inherit from Node I also had to set the name argument to None as reserved instances do not have names or tags where we can pull the Name key/value pair.

[Kami]

Thanks!

The PR looks mostly good, but I've made some minor changes after merging the patch:

1. I've modified EC2ReservedNode constructor to call parent constructor - 49e2f3b
2. I've removed unused arguments from the EC2ReservedNode constructor method - 49e2f3b
3. I've also passed size attribute to the EC2ReservedNode constructor. We can do this because list_sizes call is cheap (it doesn't result in HTTP request since sizes are stored locally in the module). - 11abec4
4. I've moved test from NimbusTests to EC2Tests class since this functionality is EC2 specific. I imagine you just looked for list_nodes tests and you accidentally put list_reserved_nodes test above it. - 1655e85
5. I've renamed list_reserved_nodes method to ex_list_reserved_nodes. Sorry if I've confused you with "you can drop the ex prefix from the class name" comment. We still use ex_ prefix, but only for method and argument names.

[cderamus]

Ah, thanks for that and good call on the list_sizes.