Malformed URI fix

I had a production site up for a few days, and it went down with this message:

```
URIError: URI malformed
    at decodeURI (native)
    at exports.Server.serve (/var/sites/zoejs.org/node_modules/zest-server/node_modules/node-static/lib/node-static.js:174:20)
    at Object.serveFiles (/var/sites/zoejs.org/node_modules/zest-server/zest-server.js:707:18)
    at Timer.list.ontimeout (timers.js:101:19)
```

It seems that the decodeURI function can have an invalid input!

So I added a try-catch statement around this line. I haven't been able to test this as I don't have the string that caused the issue, but I believe this should resolve the issue from happening again.

Suggestions welcome.