fix(cli): convert patterns from array to string

When specifying `specs` on the command line like this:
`protractor --specs e2e-tests/*.js`

Optimist automatically resolves these patterns and converts `argv.specs` into an array:

```
[ 'e2e-tests/**/*.js',
  '/Users/Robbin/Development/angular-seed/e2e-tests/scenarios.js' ]
```

The function `processFilePatterns_()` tries to split `argv.specs`, which doesn't work obviously as it's an array. This adjustment fixes this and allows Protractor to run without configuration file.