Merge pull request #707 from hagenburger/master

Add import paths instead of resetting them
Fix error with link_to when options are nil
Fix Middleman::Util.extract_response_text to follow the Rack spec (and thus work with rack 1.4.3)
Merge pull request #717 from bhollis/rack

Fix Middleman::Util.extract_response_text to follow the Rack spec (and thus work with rack 1.4.3)
Merge pull request #714 from bhollis/link_to

3.0.8/3.0.9 breaks middleman-blog's `tag_path` method
added font file types to asset_hash extension