Move 2.7 to 2 (#635)

Closes #579.

stdlib/2/heapq.pyi

@@ -0,0 +1,15 @@
+from typing import TypeVar, List, Iterable, Any, Callable
+
+_T = TypeVar('_T')
+
+def cmp_lt(x, y) -> bool: ...
+def heappush(heap: List[_T], item: _T) -> None: ...
+def heappop(heap: List[_T]) -> _T:
+    raise IndexError()  # if heap is empty
+def heappushpop(heap: List[_T], item: _T) -> _T: ...
+def heapify(x: List[_T]) -> None: ...
+def heapreplace(heap: List[_T], item: _T) -> _T:
+    raise IndexError()  # if heap is empty
+def merge(*iterables: Iterable[_T]) -> Iterable[_T]: ...
+def nlargest(n: int, iterable: Iterable[_T]) -> List[_T]: ...
+def nsmallest(n: int, iterable: Iterable[_T]) -> List[_T]: ...