Use `response.content` for binary response content

[SpainTrain]

Would you accept a PR to update process_pdf_response and process_zip_response (https://github.com/housecanary/hc-api-python/blob/master/housecanary/output.py#L91) to use response.content, as is suggested for binary response content (http://docs.python-requests.org/en/master/user/quickstart/#binary-response-content)? Is there a reason to use .text?

This would require a major bump, but would make the library more intuitive to work with.