fix for issue python-hyper#394

issue python-hyper#394 Port Number is not present in the authority header
based on https://tools.ietf.org/html/rfc7540#section-8.1.2.3 and https://tools.ietf.org/html/rfc3986#section-3.2.3

Author: alexpayne482

Diff for: hyper/http20/connection.py

@@ -505,7 +505,8 @@ def putrequest(self, method, selector, **kwargs):
         # ":path". We can set all of these now.
         s.add_header(":method", method)
         s.add_header(":scheme", "https" if self.secure else "http")
-        s.add_header(":authority", self.host)
+        port = "" if ((self.secure and self.port == 443) or (not self.secure and self.port == 80)) else (":" + str(self.port))
+        s.add_header(":authority", self.host + port)
         s.add_header(":path", selector)
 
         # Save the stream.