Normalizing some options now that noZepto

Hi @tylersticka

I'm seeing a couple of values getting computed for default options that I think are partially vestigial from Zepto. Specifically:

```
duration: ($.fx !== null) && ($.fx.cssPrefix !== null) ? $.fx.speeds._default : 400,
```

and

```
cssPrefix: ($.fx !== null) && ($.fx.cssPrefix !== null) ? $.fx.cssPrefix : '',
```

Not a lot of Google hits for `$.fx.cssPrefix` but it does appear to be Zepto-related. What are sane defaults for these now that `jQuery` is the only game in town?