middleware: upgrade to v0.5.0 format

[jonschlinkert]

(team @doowb and I can do most of these, no need to worry about converting, we just wanted to keep everyone informed, // cc @assemble/core-team)

• plugin upgrade instructions (@doowb) (once @doowb or I post the upgrade instructions please feel free to add your comments or add additional info if we missed anything)

The following plugins need to be updgraded to the Assemble v0.5.0 format. Let @doowb or I know if you need help with the conversion.

• assemble-contrib-anchors
• assemble-contrib-anchors-example (move to gh-pages branch of anchors plugin)
• assemble-contrib-contextual
• assemble-contrib-decompress
• assemble-contrib-download
• assemble-contrib-drafts
• assemble-contrib-i18n (in progress @doowb)
• assemble-contrib-lunr
• assemble-contrib-lunr-examples (move to gh-pages branch of lunr plugin)
• assemble-contrib-navigation (@jonschlinkert)
• assemble-contrib-pagination (@doowb) deprecating?
• assemble-contrib-permalinks: Generalize into a lib with an interface that can be used by other plugins (and non-assemble projects)
• assemble-contrib-permalinks
• assemble-contrib-rss (@pburtchaell)
• assemble-contrib-sitemap (@hariadi)
• assemble-contrib-toc
• assemble-contrib-toc-example (move to gh-pages branch of toc plugin)
• assemble-contrib-wordcount

Plugin conventions

• main property in package.json should be index.js. please name/rename the main file to index.js
• on the exported function, use next(), not done() or cb() etc.

[tkrugg]

assemble-contrib-contextual Readme file example still uses
plugins: ['assemble-middleware-contextual', 'other/plugins/*.js']

[jonschlinkert]

closing since this refers to an outdated version of grunt-assemble and is not relevant to the current assemble