make websocket-client dependency more open

fixes: #413

The issue as reported in #262
was not reproduced in versions of websocketclient over 0.43.0, so just mask
the known bad versions.  This allows consumption of possible security fixes and
allows the client to be co-installable with more python libraries.

Author: prometheanfire

requirements.txt

@@ -6,6 +6,6 @@ urllib3>=1.19.1,!=1.21  # MIT
 pyyaml>=3.12  # MIT
 google-auth>=1.0.1  # Apache-2.0
 ipaddress>=1.0.17  # PSF
-websocket-client>=0.32.0,<=0.40.0 # LGPLv2+
+websocket-client>=0.32.0,!=0.40.0,!=0.41.*,!=0.42.* # LGPLv2+
 requests # Apache-2.0
 requests-oauthlib # ISC