allow client to disconnect when handlers are done

added a waitgroup on websocketClient to keep track of handler
goroutines specific to the client
IMPORT PATH MODIFICATION CHANGESET
----------------------------------

Please use this changeset as the first one on top of the conformal codebase.
Note that if there are new imports, they need to be changed as part of this
changeset. In general, use "git rebase" on github.com/conformal's version
and apply this changeset first.
Task #396 on Task Board:

Create a stub websocket call getdepositscript.