YAML Configuration for Publications is Too Complicated

[kmdalton]

We should

• streamline the way we use YAML for publications.
• only need to change one file to add a pub. (right now we have to edit publications.md and _data/publications.yml).

See this comment by @tj.

this list. it's not an issue for this PR perhaps, but:

• the leading comma feels like a "gotcha"
• shouldn't it be a YAML list of strings, one entry per author, rather than a string with commas?

Originally posted by @tjlane in #46 (comment)