Merge branch 'stable-2.12'

* stable-2.12:
  Add a test for Asciidoctor document titles / sections
  Add correct license for asciidoctor
  Make the basicTextFormattingWorks() test more strict
  Add tests to check that empty input renders to empty output
  AsciidoctorFormatterTest: Fix order of expected and actual results
  AsciidoctorFormatterTest: Do not pass baseDir to AsciidoctorFormatter()
  AsciidoctorFormatter: Simplify code by using the Asciidoctor >= 1.5 API
  Upgrade asciidoctor and its jruby dependency
  Add a unit test for the AsciidoctorFormatter
  Upgrade asciidoctor and its jruby dependency
  MarkdownFormatterTest: Fix order of expected and actual results
  MarkdownFormatterTest: Make a few member variables local ones
  xdocs: Add a unit test for the MarkdownFormatter

Change-Id: I99578f15906a3fa7a75d9ea500d502f1948b8720