Add jekyll-thumbnail-filter to plugins list
Use relative path for `path` Liquid variable in Documents
Keep backwards compatibility

Re-add `relative_path` Liquid variable too keep compatibility
Allow Enumerables to be used with "where" filter.
where filter - test return value when filtering a Hash
Add rbtrace and stackprof and a script/benchmark script.
Link atom feed from html head

This makes it possible for browsers to autodiscover the feed. Fixes https://github.com/jekyll/jekyll/issues/2995
Merge pull request #2993 from jekyll/benchmarking
Update history to reflect merge of #2993 [ci skip]
Move script/benchmark to script/stackprof. [ci skip]
Cache the extname regexp in Converters::Markdown and Textile
Cache variables that won't change through the life of an object
Only compile the Converter#matches regexp when asked for
Add test for Document#basename_without_ext
Only run script/bootstrap in stackprof if stackprof executable isn't there
Cache the `@includes_dir` in each instance so the method isn't called all the time
Don't print the location of the stackprof executable
Only re-run the stackprof if I delete the prof output file.
Ignore the stackprof tmp files.
Fix feed link to respect baseurl