Add doc to warn about strange behaviour with assets path when using directory indexes.
Fixes middleman/middleman#818
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Shamelessly add AlpineLab website to "Sites built with Middleman" page
Merge pull request #231 from michaelbaudino/add-alpinelab-site

Shamelessly add AlpineLab website to "Sites built with Middleman" page
Add omegaverse.info to sites built with middleman
Merge pull request #232 from movitto/add-site

Add omegaverse.info to sites built with middleman
Added the new Sass (official) website to the list.
Merge pull request #234 from bpainter/master

Added the new Sass (official) website to the list.
Merge pull request #230 from michaelbaudino/document-directory-indexes-relative-assets-path-bug

Add doc to warn about strange behaviour with assets path when using diretory indexes.
Fix code example

Remove unnecessary div element in code example.
Merge pull request #236 from theluckyzombie/master

Fix code example
Document Custom collections feature
Document custom frontmatter data in permalinks
Merge pull request #237 from dgalarza/blog/custom-collections

Blog/custom collections
Merge remote-tracking branch 'upstream/master' into ja

Conflicts:
	source/blogging.html.markdown
	source/pretty-urls.html.markdown