Update webrick to version 1.8.2 (#677)

Author: depfu[bot]

Gemfile.lock

@@ -301,7 +301,7 @@ GEM
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
-    webrick (1.8.1)
+    webrick (1.8.2)
     websocket (1.2.11)
     websocket-driver (0.7.6)
       websocket-extensions (>= 0.1.0)