Add ability to specify an alias for a given request param

This allows us to call params with the more familiar Ruby
case/capitalization. For instance, defining the following:

param :imageRef, alias: :image_ref

in a request file makes the following possible:

session.compute_service.request :create_server do |params|
  params[:imageRef] = 'something'
end

session.compute_service.request :create_server do |params|
  params.image_ref = 'something'
end

NOTE: At this point, params can only be called via method
calls and not via the [] accessor.
Add aliases to camelCased params
Merge pull request #57 from relaxdiego/feature/28

Add ability to specify an alias for a given request param
    
This allows us to call params with the more familiar Ruby
case/capitalization. For instance, defining the following:
    
param :imageRef, alias: :image_ref
    
in a request file makes the following possible:
    
    session.compute_service.request :create_server do |params|
      params[:imageRef] = 'something'
    end
    
    session.compute_service.request :create_server do |params|
      params.image_ref = 'something'
    end
    
NOTE: At this point, params can only be called via method
calls and not via the [] accessor.