RangeSet("2-10").monotonic gives a wrong result of "False". Fix the bug
and add more tests into test_rangelib.py.
Change-Id: I04780571b45ecafd34040f405756b9745a9e21a5
Separate the test cases in rangelib.py comments into a python unittest
file.
To invoke:
$ python -m unittest test_rangelib
Change-Id: I59e4ce0aaccc83bcbb42fee15775683dcd559d99