Docx reader: handle empty reducibles.
Docx reader test: Add an emphasized space to normalize test.

This should be ignored, so the output should be the same as the previous
test.
Merge pull request #1521 from jkr/emptyEmph

Discard empty formatters
EPUB reader:  use walk instead of bottomUp.

This should be more efficient.
Add dropCap to paragraph style.
Docx reader: Use dropcap state.

If we get to a dropcap, we keep hold the inlines until the next
paragraph, and combine it there.
Docx: Add dropcap tests.
Docx reader: combine inlines properly in dropcaps.

Make sure that adjacent inlines are combined properly in dropcaps. This
updates the test results as well.
Merge pull request #1522 from jkr/dropCap

Drop cap
Docx reader: Make dropcap combining more efficient.

Before, we had to run reduceList on the whole combined paragraph, which
was redundant, and could take some time for long paragraphs. We only
need to combine the drop cap with the first inline of the next
paragraph.
Merge pull request #1523 from jkr/dropCap2

Docx reader: Make dropcap combining more efficient.