Add Pithub::Test to hold uri_is()

uri_is() is necessary to make testing URIs with queries easier.  Their
order cannot be predicted.
Add a default per_page, same as the Github default.

The Github default per_page is 30.  This is an incremental change just
to find all the things which break if there's a default per_page
even if the Github behavior is the same.

Next commit will try changing it to 100.
Change the per_page default to 100.

Fix the tests.  This is a cosmetic test fix.  The fixture data is now probably wrong,
it doesn't know about the per_page being changed to 100.

The live tests use 4 less API calls, so that's nice.
Merge pull request #167 from plu/feature/per_page=100

per page=100