Accept a b flag in 'comments'

The default ftplugin/python.vim uses the b flag. I am unsure what other
flags are needed to be added to the pattern. From my reading of :help
'comments' this should be enough. I guess I'll just have to add them as
issues appear.

plugin/double-tap.vim

@@ -35,7 +35,7 @@ endif
 let g:loaded_doubletap = 1
 " }}}
 
-let s:pattern = '\(,\|^\):\zs\([^,]\+\)' " This patterns finds the wanted
+let s:pattern = '\([b,]\|^\):\zs\([^,]\+\)' " This patterns finds the wanted
                                          " item in 'comments'
 
 let s:commStart = {} " dict to hold the comment starters using