Show spinner while queries are executing

Fixes #235 

Here's what it looks like (I artificially added 2s of latency to make it more obvious):
![cql spinner](https://cloud.githubusercontent.com/assets/98301/5306116/a762c3ba-7bcf-11e4-995a-a0d93617af5c.gif)

(I also took the opportunity to delete some unused code.)
Changed it to:

```
// Ignore all currently pending requests (presumably because there's a newer one).
```

Is that any clearer? The upshot is that there may be pending requests, but there's a new query, so those pending requests are irrelevant and should be ignored when they come back.