Add macro to reorder lines by length.

Hi,

This is my macro to reorder selected lines by length. It makes, for example, the code:

```python
from django.core.urlresolvers import reverse
from django.template.loader import render_to_string
from django.template import Context, Template
from celery.task import task
```

become

```python
from celery.task import task
from django.core.urlresolvers import reverse
from django.template import Context, Template
from django.template.loader import render_to_string
```

How to use: Select the lines, then run the macro.