Ensure that the format param is always appended to paged catalog urls

[eliotjordan]

Closes #97

[coveralls]

Coverage increased (+0.002%) to 97.903% when pulling a58ee6c on 97-json-format into 07914db on master.

[coveralls]

Coverage increased (+0.002%) to 97.903% when pulling a58ee6c on 97-json-format into 07914db on master.

[coveralls]

Coverage increased (+0.002%) to 97.903% when pulling a58ee6c on 97-json-format into 07914db on master.

[jkeck]

Thanks @eliotjordan, this worked on all the sites that I had tested, but clearly there are some differences to how some the APIs work (which is a bit troublesome). Thanks for making the fix.