Fix CollectionDecorator#respond_to? for non AR collections

[catks]

Description

Draper::Collection#respond_to? does not work properly when using a non AR object, eg:

class FooDecorator < Draper::Decorator; end  

decorator_collection = FooDecorator.decorate_collection([Object.new])
decorator_collection.respond_to?(:limit) #=> true
decorator_collection.limit(10) # Raises NoMethodError: undefined method `limit' for []:Array   

I think decorator_collection.respond_to?(:limit) should return false for these cases

Testing

1. Create a empty decorator with: class FooDecorator < Draper::Decorator; end
2. Initialize a non AR collection with it: decorator_collection = FooDecorator.decorate_collection([Object.new])
3. decorator_collection.respond_to?(:limit) should return false

To-Dos

• tests
• documentation

References

• GitHub Issue ####
• GitHub Pull Request ####