Proof of concept example for multiple allocations JSON-only API.

This is in no way ready for merge but it's an example of how to integrate Chargify's allocations api with ActiveResource .. sort of.

Usage example:

```ruby
# Set all components to 100 allocations
s = Chargify::Subscription.find xyz
components = s.components
components.each do |c|
components.allocated_quantity = 100
end
s.allocate_components components
```

It receives an array of Component objects and does the submission to Chargify to update those components. Works perfectly except for the response. In this case ActiveRecord expect's the POST response (which is in REST terminology a CREATE action) to return attributes for *one* resource not an *array* of resources, so ActiveRecord freaks out when it receives an array of allocations from Chargify.

I overloaded the method ActiveRecord uses to read the response after `create` to interpret Chargify's response, but it's a pretty ugly as heck hack.

Anyways, food for thought, any ideas how to get around the non-RESTful nature of this API is more than welcome.