Add fixtures for pandoc 1.12.
Make the PandocImporter support the new Pandoc API (v1.12).
Create figures instead of images.

We should consolidate the types.
Either make images capable of captions, making them
Composite nodes, or stay with figures.
Make the PandocExporter compatible with API version 1.12.
Import the yaml-meta block with PandocImporter.
Add example files for extended Pandoc Markdown content.
First step towards importing formulas.

Not yet working. Needs better strategy for dealing
with children elements of "Para".
Fixed pandoc importer to support rich paragraphs.
Import Pandoc Markdown tables.
Updated package.json
Add missing require.
Fix pandoc converter to reflect change in Figure node.
Store labels of headings as source_id for cross references.
Add try catch block around importer call.
Fix latest change in Pandoc JSON format.

Actually, the format changed 'inadvertantly' as the underlying
json library 'aeson' did.
JGM changed pandoc so that the older format (as with pandoc 1.11) is generated.
Removed obsolete fixtures.
Fix PandocImporter and Exporter to support old format.
Fix regression.
Display stacktrace on errors.