fix frontmatter

[john-science]

The Jekyll front matter in each post needs to be changed to:

• layout - used for theme layout and post-type for front page
• tagline (rename to "title") - each post needs a title
• tags (rename to "topics") - so I can have a topics section
• summary - to display on front page
• date? - 'last-modified date' so I can control post order and freshness???

[john-science]

Several commits last night fixed this issue. The front matter is now much more regular and conforms to the new site organization.