Inconsistent handling of undefined URL params

[seriema]

While working on #44 to raise test-coverage I noticed that empty URL params were handled differently depending on if it's an undefined property on the $http config object, or if it's just an empty value in the URL.

Test cases

Case 1: empty value in URL

defaultRequest.url = '/api/pokemon?releaseDate';

becomes
/mock_data/pokemon/releasedate=.get.json.

Case 2: undefined value in object

defaultRequest.url = '/api/pokemon';
defaultRequest.params = {
  'releaseDate': undefined
};

becomes
/mock_data/pokemon/releasedate=undefined.get.json

Wanted result

= and =undefined are both unwanted in a file name IMHO. So it should be completely removed. I.e. expected file path would be /mock_data/pokemon/releasedate.get.json.

[seriema]

It could be considered a breaking change and thus a major version bump, but I see it as undefined/unexpected/undocumented behaviour. So if someone's relying on it it wasn't safe, and fixing this should make it better for everyone.