fix call signature of Domain.delete_record

fixes this error in the test suite:

        def delete(self):
    >       return self.domain.delete_record(self.id)
    E       TypeError: delete_record() missing 1 required positional argument: 'record'

    skiff/Domain.py:25: TypeError
tests: fix pagination tests (20 results are returned by default, not 10)
fix 'search' logic in Image.get

Was causing this error in the test suite:

    _____________________________________ TestImages.test_get ______________________________________

    self = <test_skiff.TestImages object at 0x7f747617afd0>

        def test_get(self):
            # test string search
    >       img = s.Image.get("Ubuntu")

    test_skiff.py:105:
    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
    skiff/Image.py:79: in get
        r = skiff.get('/images/%s' % (iid))
    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    self = <skiff.utils.SkiffClass object at 0x7f74783b0ba8>, url = '/images/Ubuntu', action = None
    params = {'page': True}

        def get(self, url, action=None, params=None):
            if not params:
                params = {
                    'page': True
                }

            collection = []
            r = requests.get(DO_BASE_URL + url, params=params, headers=self.DO_HEADERS).json()

            if 'message' in r:
    >           raise ValueError(r['message'])
    E           ValueError: The resource you were accessing could not be found.

Also change the behavior of search. Previously it would have returned
the first name that matched, now it returns the shortest name that
matches.

For example, 'Ubuntu' would have returned 'Ruby on Rails on Ubuntu 14.04
(Nginx + Unicorn)', and now it returns 'Ubuntu 14.04 x64'. Logic for
this being that most people would expect 'Ubuntu' to return a base
ubuntu image, not an ubuntu image with rails + nginx + whatever.
tests: allow user to pass in their own test domain

Seems domains are tied to accounts. I couldn't get the tests to run
with 'mysuperrandomdomainname.com'. Was getting these errors:

    ValueError: No Suitable Domain Found
tests: use nyc2 region instead of nyc1

DO site says that nyc1 is disabled to due high demand
'iteritems' is just called 'items' in python 3