ListIntSet implementation works. Test output ->

-> Test output now gives results for linked list as well.
Results are identical (as they should be). Except that
the list implementation uses far more comparisons to
perform contains (and this will scale badly as the list gets
longer).

....
$ java TestIntSets
Run tests on TreeIntSet:
add 7 to the set
add 9 to the set
add 7 to the set again!
print the set contents: 7, 9
verbose test whether set contains 9:
	contains checks 9 against 7
	contains checks 9 against 9
	Result set does contain 9
extend set to: 7, 3, 1, 9, 8, 49, 13, 29, 22, 21, 19, 14, 18, 23, 27, 26, 45, 35, 34, 33, 37, 41, 39, 43, 44, 50
verbose test whether set contains 19:
	contains checks 19 against 7
	contains checks 19 against 9
	contains checks 19 against 49
	contains checks 19 against 13
	contains checks 19 against 29
	contains checks 19 against 22
	contains checks 19 against 21
	contains checks 19 against 19
	Result set does contain 19
verbose test whether set contains 28:
	contains checks 28 against 7
	contains checks 28 against 9
	contains checks 28 against 49
	contains checks 28 against 13
	contains checks 28 against 29
	contains checks 28 against 22
	contains checks 28 against 23
	contains checks 28 against 27
	Result set does not contain 28

Re-Run the same tests on ListIntSet:
add 7 to the set
add 9 to the set
add 7 to the set again!
print the set contents: 7, 9
verbose test whether set contains 9:
	contains checks 9 against 7
	contains checks 9 against 9
	Result set does contain 9
extend set to: 7, 9, 3, 49, 13, 29, 45, 35, 34, 22, 23, 37, 21, 27, 41, 43, 19, 26, 8, 14, 50, 1, 33, 39, 18, 44
verbose test whether set contains 19:
	contains checks 19 against 7
	contains checks 19 against 9
	contains checks 19 against 3
	contains checks 19 against 49
	contains checks 19 against 13
	contains checks 19 against 29
	contains checks 19 against 45
	contains checks 19 against 35
	contains checks 19 against 34
	contains checks 19 against 22
	contains checks 19 against 23
	contains checks 19 against 37
	contains checks 19 against 21
	contains checks 19 against 27
	contains checks 19 against 41
	contains checks 19 against 43
	contains checks 19 against 19
	Result set does contain 19
verbose test whether set contains 28:
	contains checks 28 against 7
	contains checks 28 against 9
	contains checks 28 against 3
	contains checks 28 against 49
	contains checks 28 against 13
	contains checks 28 against 29
	contains checks 28 against 45
	contains checks 28 against 35
	contains checks 28 against 34
	contains checks 28 against 22
	contains checks 28 against 23
	contains checks 28 against 37
	contains checks 28 against 21
	contains checks 28 against 27
	contains checks 28 against 41
	contains checks 28 against 43
	contains checks 28 against 19
	contains checks 28 against 26
	contains checks 28 against 8
	contains checks 28 against 14
	contains checks 28 against 50
	contains checks 28 against 1
	contains checks 28 against 33
	contains checks 28 against 39
	contains checks 28 against 18
	contains checks 28 against 44
	Result set does not contain 28
....
write up 2.3