Document installing dependencies

@charlierudolph @allewun what do you think?
There were several reasons:
* it looked somehow weird
* the middle entry ("update") only had a single number ("1")
* none of the steps have to be done in the order printed. Actually, all of them can be done in any order.
* the bullet points separate and distinguish the steps nicely from the rest of the page

Having said all that, I don't feel strongly about this. I just wanted to see how it looks like. I like the bullet point version slightly better. But I'm cool with ordered lists if you feel strongly about this.