List rendering wrong margin

Nested list has a large `margin-top` which makes the list seems ugly. `margin-bottom` should be larger than `margin-top`.


```
* Human perceptions:
* Easy to be deceived by illusions
* Processes:
* Extraction of features (rapid)
* Pattern perception (slow)
* Memory

* Preattentive processing
* Speed is independent of number of distractors, fast (<= 10ms)
* Measurement:
* Degrees of pop out (strong effects based on color, contrast, etc)
* Degrees of difference (difference between objects in size, color)

* Conjunctions of features might be not preattentive even though there are strong differences.
```