adds test for std/sets (#1164)

Author: demotomohiro

tests/nimony/stdlib/tsets.nim

@@ -0,0 +1,25 @@
+import std/[assertions, hashes, sets]
+
+block:
+  var s = initHashSet[int]()
+  assert not s.contains(1)
+  assert not s.contains(2)
+  s.incl 2
+  assert not s.contains(1)
+  assert s.contains(2)
+  s.incl 3
+  assert not s.contains(1)
+  assert s.contains(2)
+  assert s.contains(3)
+  assert s.containsOrIncl(2)
+  assert not s.containsOrIncl(5)
+  assert s.containsOrIncl(5)
+  s.excl 5
+  assert not s.contains(5)
+  assert not s.containsOrIncl(5)
+  assert s.contains(5)
+
+  var p = 1
+  for i in items(s):
+    p = p * i
+  assert p == 30