Put margins on the bottom of block elements
Put margins on the bottom of block elements

Currently our spacing works like:

```
--------------------------
|//////// margin ////////|
|text text text text text|
|//////// margin ////////|
|text text text text text|
|text …                  |
```

This means that elements will be offset from the top of the page if they
are the first thing on the page. This is bad because, visually, it looks
like the margins are wrong, and it doesn’t line up with the output we
get from DVLA.

This commit changes the margins to go underneath,
like so:

```
--------------------------
|text text text text text|
|//////// margin ////////|
|text text text text text|
|text …                  |
|//////// margin ////////|
```

So the lines of text are still spaced apart by the same amount, but
start from the edge of the page’s top margin.

alphagov/notifications-utils