For now, allow all characters in stream names.

We've had multiple requests from MIT zephyr users to allow
non-alphanumeric stream names, and we haven't decided what we want to
allow, so for now allow everything.

Note that the web client and mirror script limit stream names to 30
characters, which is our database limit.

(imported from commit 2acb5ee04e5ee7c40031ac831e12d09d04bbb2e6)

bots/zephyr_mirror.py

@@ -512,7 +512,7 @@ web interface.
             print
 
 def valid_stream_name(name):
-    return re.match(r'^[\w.][\w. -]*$', name, flags=re.UNICODE)
+    return True
 
 def parse_zephyr_subs(verbose=False):
     zephyr_subscriptions = set()