Filter non-member properties in watchIgnorePatterns to avoid minmatch parse exception

Avoid minimatch throw exception when watchIgnorePatterns is array with custom function perperty

eg:
I first extend the Array prototype.
```javascript
Array.prototype.diff = function() {}
```

Then when I use forever with option watchIgnorePatterns=[], and change some file under watch.

The minimatch complain
```javascript
node_modules/forever-monitor/node_modules/minimatch/minimatch.js:34
    throw new TypeError("glob pattern string required")
```