Keep client connections alive using Network.WebSocket.forkPingThread.
Bump yesod-websockets version.
Fix if then statement layout in Scaffolder.

Fixes the Travis build error:

```
Scaffolding/Scaffolder.hs:99:34:
    Unexpected semi-colons in conditional:
        if isBare; then LT.replace "cd PROJECTNAME && " ""; else LT.replace
                                                                   "PROJECTNAME" (LT.pack project)
    Perhaps you meant to use -XDoAndIfThenElse?
```
Depend on websockets >= 0.9 in yesod-websockets.cabal.

The forkPingThread function was added in version 0.9 of websockets.

Complimentary fix to #889.
Merge pull request #889 from creichert/master

Keep client WebSocket connections alive using Network.WebSockets.forkPingThread