Mark anonymous endpoints in API docs

I noticed some of the endpoints allow anonymous access with no API key required.

```
/bmarks
/:username/bmarks
/bmarks/popular​
/:username/bmarks/popular
/bmarks/search
/:username/bmarks/search
/:username/tags/complete
```

Also, `/bmarks/popular​` was using the same description and example as `/:username/bmarks/popular`.