adds failing tests for issue #2: equal sign in cookie value
implements values that can contain '=' for new and delete; fixes tests

`get` is still non-functional, and has failing tests. `new` and
`delete` are working.
fixes issue #2: equal sign in cookie value

`get` was already working, but the tests were incorrect. Adds a few
more tests to be sure, but they are likely redundant. Cookie value can
now contain any number of '=' signs.