Add my three publish plugins

metalsmith-datamarkdown - Use markdown content within html tags via data-markdown attribute
metalsmith-wordcount - Compute wordcount / average reading time
metalsmith-headingsidentifier - Add an id and anchor to all headings on a page. Ideal for permalinks.
Renamed packages

Renamed packages as suggested by @ianstormtaylor. (Also removed and republished them on npm).
Merge pull request #61 from majodev/patch-1

Add my three published plugins