Use Bootstrap media object for listing comments

http://twitter.github.com/bootstrap/components.html#media

- Introduce lib/comments.php: contains Roots_Walker_Comment

- Update templates/comments.php to use the new walker, general
clean up
Merge pull request #683 from retlehs/bs_media_object_comments

Use Bootstrap media object for listing comments
Ref #652 - Add installation/config info to docs TOC
Remove disabled post nav links
Add section about grunt to README
Simplify alerts
Update editor-style.css

- Bring in latest Bootstrap changes

- Add instructions on how to update the file
Update danish lang files
Update CHANGELOG with changes since 6.3.0
Comments clean up, consistent formatting
Update doc/usage.md

HTML5 Boilerplate documentation link was incorrect.  
Merge pull request #687 from ShutterBrandon/patch-1

Update doc/usage.md
Root relative URLs
comment
added conditional
Fix (hack) for subdir installs
Merge pull request #688 from damianregan/relativeurls

Relative URL fixes
Fix for admin bar
Merge pull request #691 from damianregan/relativeurls

Fix for admin bar
Update lib/h5bp-htaccess

Removed redundant duplication comment. Just a tiny a tiny thing