Add support for prev/next/self links when returning paginated results. To do this: 1) change "data" envelope from an array to a dict 2) move the "data" array to the "collection" property, which is an array of elements in the collection. 3) add @links dict keyed by link relation: self, next, prev. Each relation is an array of dicts with uri and rel keys. In this case there is only one element, but there is nothing preventing a relation from having multiple url's. So this follows the formatting needed for the general case. Relations are present only if it makes sense. So first page has no prev and last page has no next. 4) add @total_size with number of element selected if they were not paginated. Replicates data in X-Count-Total header. Changed index to start at 1. So the first page is page_index 1 and not page_index 0. (So I am no longer surprised when I set page_index to 1 and am missing a bunch of records 8-)). Also a small fixup, json response ends with a newline so printing the data, or using curl makes sure that anything printing after the json output (like shell prompts) is on a new line. Tests added for all cases.

class MockNull:
    def __init__(self, **kwargs):
        for key, value in kwargs.items():
            self.__dict__[key] = value

    def __call__(self, *args, **kwargs): return MockNull()
    def __getattr__(self, name):
        # This allows assignments which assume all intermediate steps are Null
        # objects if they don't exist yet.
        #
        # For example (with just 'client' defined):
        #
        # client.db.config.TRACKER_WEB = 'BASE/'
        self.__dict__[name] = MockNull()
        return getattr(self, name)

    def __getitem__(self, key): return self
    def __bool__(self): return False
    # Python 2 compatibility:
    __nonzero__ = __bool__
    def __contains__(self, key): return False
    def __eq__(self, rhs): return False
    def __ne__(self, rhs): return False
    def __str__(self): return ''
    def __repr__(self): return '<MockNull 0x%x>'%id(self)
    def gettext(self, str): return str
    _ = gettext