Add type annotations for emoji (#1506)

This adds type annotations for [`emoji` library](https://github.com/carpedm20/emoji/)

third_party/2and3/emoji.pyi

@@ -0,0 +1,18 @@
+from typing import Tuple, Pattern, List, Dict, Union
+
+_DEFAULT_DELIMITER = ...  # type: str
+
+def emojize(
+    string: str,
+    use_aliases: bool=...,
+    delimiters: Tuple[str, str]=...
+) -> str: ...
+
+def demojize(
+    string: str,
+    delimiters: Tuple[str, str]=...
+) -> str: ...
+
+def get_emoji_regexp() -> Pattern: ...
+
+def emoji_lis(string: str) -> List[Dict[str, Union[int, str]]]: ...