• Atom feeds output <content> in addition to <summary>
• Atom feeds use <published> for the original publication date and
  <updated> for modifications
• Simplify Atom feed ID generation and support URL fragments
• Produce category feeds with category-specific titles
• RSS feeds now default to summary instead of full content —
  set RSS_FEED_SUMMARY_ONLY = False to revert to previous behavior
• Replace MD_EXTENSIONS with MARKDOWN setting
• Replace JINJA_EXTENSIONS with more-robust JINJA_ENVIRONMENT setting
• Improve summary truncation logic to handle special characters and tags that
  span multiple lines, using HTML parser instead of regular expressions
• Include summary when looking for intra-site link substitutions
• Link to authors and index via {author}name and {index} syntax
• Override widget names via LINKS_WIDGET_NAME and SOCIAL_WIDGET_NAME
• Add INDEX_SAVE_AS option to override default index.html value
• Remove PAGES context variable for themes in favor of pages
• SLUG_SUBSTITUTIONS now accepts 3-tuple elements, allowing URL slugs to
  contain non-alphanumeric characters
• Tag and category slugs can be controlled with greater precision using the
  TAG_SUBSTITUTIONS and CATEGORY_SUBSTITUTIONS settings
• Author slugs can be controlled with greater precision using the
  AUTHOR_SUBSTITUTIONS setting
• DEFAULT_DATE can be defined as a string
• Use mtime instead of ctime when DEFAULT_DATE = 'fs'
• Add --fatal=errors|warnings option for use with continuous integration
• When using generator-level caching, ensure previously-cached files are
  processed instead of just new files
• Add Python and Pelican version information to debug output
• Improve compatibility with Python 3.5
• Comply with and enforce PEP8 guidelines
• Replace tables in settings documentation with data:: directives