IntervalDict items are not correctly sorted

[AlexandreDecan]

Items in an IntervalDict are sorted according to their lower bound, but when a bound is shared by two intervals (= keys), the open interval is listed first instead of the closed one:

>>> d = P.IntervalDict()
>>> d[P.open(2, 3)] = 1
>>> d
{(2,3): 1}
>>> d[2] = 2
>>> d
{(2,3): 1, [2]: 2}

The expected output should be [2] then (2, 3).

[AlexandreDecan]

Fixed in 39e2564