Add a change list function that takes any params

[katzenbar]

This allows us to access other API parmeters, like getting charges by customer or card. We are in a situation where we need to be able to look up charges by the customer id.

I had a little trouble figuring out how to write a new unit test around this. I'm not too familiar with adding new VCR cassettes to things. Any direction or help would be appreciated.

[coveralls]

Coverage increased (+0.2%) to 18.638% when pulling 594623f on ktornwall:add_charge_list_params into 0e4d31b on robconery:master.