fix spacing between deferred notes

Fix spacing between deferred notes. Fixes #3

Fix based on comment from gilgamec (see issue #3).
`\marginparpush` and `\marginskip` now work as expected on deferred notes.

Reproducible example showing the problem and validating the fix:

```latex
\documentclass{memoir}
\usepackage{lipsum}
\usepackage{marginfix}
\usepackage{color}
\marginparpush = 1cm
 \begin{document}
 \marginpar{\lipsum[2]}
 \lipsum[1]
 \marginpar{\color{red}\lipsum[2]}
 \lipsum[1]
 \marginpar{\lipsum[2]}
 \lipsum[1]
 \marginpar{\color{red}\lipsum[2]}
 \lipsum[1]
 \end{document}
```