Add tasks for all the new languages

Task/Combinations/Nim/combinations.nim

@@ -0,0 +1,21 @@
+iterator comb(m, n): seq[int] =
+  var c = newSeq[int](n)
+  for i in 0 .. <n: c[i] = i
+
+  block outer:
+    while true:
+      yield c
+
+      var i = n-1
+      inc c[i]
+      if c[i] <= m - 1: continue
+
+      while c[i] >= m - n + i:
+        dec i
+        if i < 0: break outer
+      inc c[i]
+      while i < n-1:
+        c[i+1] = c[i] + 1
+        inc i
+
+for i in comb(5, 3): echo i