Fix each/else with leading `- `

It looks like you're moving away from `-` prefixed Jade-level control structures (is that right?). However, while the following is still supported:

```jade
- each item in items
  p= item
```

…it makes sense that this is too:

```jade
- each item in items
  p= item
- else
  p no items
```

Currently this results in an 'unexpected else' error. I have updated the test to reflect this use case.

The fix involves stripping leading whitespace from the code block in the lexer, revealing that the following was already valid:

```jade
-each item in items
  p= item
-else
  p no items
```

So the thing that was unexpected was that the token's value being ` else` instead of `else`.

Hope this is alright.