Log Message:
Import commonmark-0.2.1.1

0.2.1.1
* Fix bug in prettyShow for SourceRange (#80). The bug led to an infinite
  loop in certain cases.

0.2.1
* Use official 0.30 spec.txt.
* Update HTML block parser for recent spec changes.
* Fix test case from commonmark/cmark#383. We need to index the list of
  stack bottoms not just by the length mod 3 of the closer but by whether
  it can be an opener, since this goes into the calculation of whether the
  delimiters can match.

0.2
* Commonmark.Inlines: export LinkInfo(..) [API change].
* Commonmark.Inlines: export pLink [API chage].
* Comonmark.ReferenceMap: Add linkPos field to LinkInfo [API change].
* Commonmark.Tokens: normalize unicode to NFC before tokenizing
  (#57). Normalization might affect detection of flankingness, recognition
  of reference links, etc.
* Commonmark.Html: add data-prefix to non-HTML5 attributes, as pandoc does.
* Remove unnecessary build-depends.
* Use lightweight tasty-bench instead of criterion for benchmarks.