message: docs: use `a` instead of `span` for IDs
  Apparently GitHub-flavored markdown filters out all spans.
diff: @@ -47,12 +47,11 @@ Project | Lines of CoffeeScript
  **Project builder status:** [![Build Status](https://travis-ci.org/decaffeinate/decaffeinate-example-builder.svg?branch=master)](https://travis-ci.org/decaffeinate/decaffeinate-example-builder)
  **Notes:**
  -1. <span id='autoprefixer-note'></span>
  - autoprefixer has fully moved to JavaScript via decaffeinate.
  - This build runs on the last commit before the switch to JS.
  -2. <span id='coffeescript-note'></span>
  - Some CoffeeScript tests are disabled because they are difficult to fix and
  - test cases that do not seem to come up in real-world code. See
  +1. <a id='autoprefixer-note'></a>autoprefixer has fully moved to JavaScript via
  + decaffeinate. This build runs on the last commit before the switch to JS.
  +2. <a id='coffeescript-note'></a>Some CoffeeScript tests are disabled because
  + they are difficult to fix and test cases that do not seem to come up in
  + real-world code. See
  [How decaffeinate approaches correctness][correctness-issues] for full details.
  To contribute to this list, send a pull request to the [decaffeinate-examples]
  