This looks pretty good. The only thing I don't like is the coloring of tokens in the examples. It doesn't make them easier to read; it's just distracting.
```lisp
foo
```
```
foo
```
EDIT: Submitted a PR https://github.com/alephyud/bel/pull/5
You can see what it looks like here: https://github.com/shawwn/bel/blob/085b39f5b8ee9e50b9776972b...