Support --trace in HTML reader.
HTML reader:  Fix performance issue with malformed HTML tables.

We let a `</table>` tag close an open `<tr>` or `<td>`.
Closes #1167.
ImageSize:  Use default instead of failing if image size not found

in exif header.  Closes #1358.
Markdown reader: Prevent spurious line breaks after list items.

When the `hard_line_breaks` option was specified, pandoc would
produce a spurious line break after a tight list item.  This
patch solves the problem.  Closes #1137.
LaTeX writer:  Correctly handle figures in notes.

Notes can't contain figures in LaTeX, so we fake it to avoid
an error.  Closes #1053.
MediaWiki reader: Support --trace.
MediaWiki reader: Tightened up template parsing.

The opening "{{" must be followed by an alphanumeric or ':'.
This prevents the exponential slowdown in #1033.
Closes #1033.
Markdown reader:  Support smallcaps through span.

`<span style="font-variant:small-caps;">foo</span>` will be
parsed as a `SmallCaps` inline, and will work in all output
formats that support small caps.

Closes #1360.
Docx reader tests: Introduce NoNormPandoc type.

This is just a wrapper around Pandoc that doesn't normalize with
`toString`. We want to make sure that our own normalization process
works. If, in the future, we are able to hook into the builder's
normalization, this will be removed.
Merge pull request #1361 from jkr/testNormalize

Docx reader tests: Introduce NoNormPandoc type.
Filters: don't print misleading error message.

Previously pandoc would say that a filter was not found,
even in a case where the filter had a syntax error.
Fixed compiler warnings.