Remove linebreaks when using the `${blank-name}` format

```
<bind tag="class">
  Lots 

  of 

  white space
</bind>
```

And using it in attributes like this:

```
<div class="${class}">
```

Results in:

```
<div class="
  Lots

  of 

  white space
">
```

Can linebreaks be stripped from attribute blanks?
