Allow local version identifier in wheel filenames

Fixes cases where the version part of the wheel file name would become

`0.1b1_gitbranch.buildno.1`

instead of

`0.1b1+gitbranch.buildno.1`

Fixes sdispater/poetry#756

poetry/masonry/builders/wheel.py

@@ -203,7 +203,7 @@ class WheelBuilder(Builder):
     def wheel_filename(self):  # type: () -> str
     def wheel_filename(self):  # type: () -> str
         return "{}-{}-{}.whl".format(
         return "{}-{}-{}.whl".format(
             re.sub(r"[^\w\d.]+", "_", self._package.pretty_name, flags=re.UNICODE),
             re.sub(r"[^\w\d.]+", "_", self._package.pretty_name, flags=re.UNICODE),
-            re.sub(r"[^\w\d.]+", "_", self._meta.version, flags=re.UNICODE),
+            re.sub(r"[^\w\d.\+]+", "_", self._meta.version, flags=re.UNICODE),
             self.tag,
             self.tag,
         )
         )