Blog archive pages for guest authors and former employees

[gboone]

Right now guest authors and people who leave 18F don't get an archive of blog posts they authored for us. I'd be great for our own tracking purposes and for alums to have a easy list to point at to have these archive pages.

We get archives for current team members at /team/<name>/ (where name matches a common name field in _team and _data/authors.yml. If no file matches _team/<name>.md for an author, no page generates. If the author has a url listed, we link to that url on the blog post. It'd be great if instead we generated a /author/<name>/ page with the author's full name, a list of blog posts, and maybe some indication they're a guest or alum.

Feature: All authors of blog posts should have an archive of their writing
  Readers should be have a reference for all posts written by an author, regardless of whether they work for 18F right now.
  Authors are kept in a data file located at `_data/authors.yml`. Current team members have a file in `_team`, that file generates an archive at `/team/<name>.
  The final solution should 
  1. Ensure `_data/authors.yml` contains all authors
  2. Generate an archive page for every author listed in `_data/authors.yml` with a url structure: `/author/<name>`
  3. The [default_profile](https://github.com/18F/18f.gsa.gov/blob/master/_layouts/default-profile.html) layout can be used or adapted for the archive template

Scenario: A guest author or former team member writes a blog post for 18f.gsa.gov
Given the author is listed in `_data/authors.yml`
When I click on the author's name on the blog post
Then I am taken to a page listing all the posts written by that author.

Scenario: An 18F team member writes a blog post for 18f.gsa.gov
Given the team member is listed in `_data/authors.yml`
When I click on the team member's name on the blog post
Then I am taken to a page listing all the posts written by that team member

Scenario: Builds fail if all authors on a post are not found
Given a blog post is drafted
  And one or more of the post's authors are not listed in `_data/authors.yml`
When I issue a pull request or build the site
Then Jekyll will fail to build 
  And a descriptive error will be printed in the console

Scenario: Author links should have a predictable URL
Given A team member leaves 18F
  And that team member has written >= 1 blog posts
When I click on the team member's name or otherwise navigate to their archive page
Then I am taken to a page listing all the posts written by that team member

Scenario: Existing links to team member profiles should redirect to their blog archive
Given a user navigates to an existing team profile page (example: /team/boone/)
When The page loads
Then the user should be redirected to their author profile page (example: /author/boone)

[elainekamlley]

Steps:

• Change URL and ensure it is redirecting properly from /team to author
• Specify an attribute to indicate alum (ask team if we want to track detailees)
• Ensure the build fails if author is not found
• Move author archive to tag layout

[coreycaitlin]

I'm inclined to vote against tracking detailees — that seems complicated and hard to explain!