Fix baseurl default in the docs

Display the new baseurl default (commit: [97e9fb2](https://github.com/jekyll/jekyll/commit/97e9fb29b09fcd67f960000bea3af88f8d5bfab2)) in the docs.
Use kramdown.
Pure JavaScript for adding anchors.
Add font-awesome & Ben's CSS
Use HTML and CSS we just created.
Add font-awesome web fonts.
Merge pull request #2341 from albertogg/fix-baseurl-default-in-docs
Update history to reflect merge of #2341 [ci skip]
Add newlines, duh.
Merge pull request #2342 from jekyll/anchor-links
Update history to reflect merge of #2342 [ci skip]
Use symbol instead of HTML number in upgrading.md
Fix case #2349
Fix link to frontmatter defaults docs
Added item_property to where filter
Add test for using where filter on collections
Merge pull request #2351 from yizeng/#2349/fix-escaping
Update history to reflect merge of #2351 [ci skip]
Merge pull request #2353 from gpxl/configuration-defaults-typo
Update history to reflect merge of #2353 [ci skip]
Merge pull request #2359 from abroder/where-collection