Add support for more options

`options.options` might be a bit confusing but it would look like this:

```js
pygmentize({ lang: 'js', format: 'html', options: 'startinline=1' }, 'var a = "b";', function (err, result) {
  console.log(result.toString())
})
```

Which makes sense since it matches up with how you'd call pygments from the command line.

Note, I could have kept more of the existing code structure by doing the following:

```js
 var execArgs = [
              '-f', options.format || defaultFormat
            , '-l', options.lang || defaultLang
            , '-P', 'encoding=' + (options.encoding || defaultEncoding)
            , '-O', options.options || "''"
          ]
```

But thought that might be a bit dirty.