Update _top_bar.css to respect font-size overrides

The font-size of links in a top-bar section was hard set to 13px and did not respect any overrides set by the user.
Merge pull request #1641 from TheVole/patch-1

Update _top_bar.css to respect font-size overrides
added links to 3.0 and migration guide from getting started page
Merge branch 'master' of github.com:zurb/foundation
uses topbar-link-weight variable
Merge pull request #1643 from jessepollak/fix-topbar-link-weight

Uses $topbar-link-weight variable to set the topbar link weight
Update _block-grid.scss

Adds a variable $block-grid-media-queries to control whether class styles are processed. For those who are only using mixins to define grid behavior, this may be set to false to lighten the output file.
fix html markup example on docs
Merge branch 'master' of github.com:zurb/foundation
Update section docs.
Merge changes.
Fix html rendering issues on joyride page, and fix typo on dropdown docs.
Remove erroneous comma in dropdown.js
Return true if ie8compat in section small test.
updated support page and a topbar style bug
Merge branch 'master' of github.com:zurb/foundation
updated sass page links
fixed typo in keystrokes
Update block-grid.html.erb

Added new $block-grid-media-queries variable to documentation.
update typography styles to change from small to large breakpoint a bit. Mostly headers