Previously normalisation was handled by the `normalizeSpaces` function. The behavoir of the builder monoid is slightly different and melds together more items such as consecutive strings and spaces adjacent to line breaks. The tests have been changed to reflect this.
All relevant tests passed when the string melding line of the builder monoid was commented out.
The _note attribute is supported. This is unofficial, but
used e.g. in OmniOutliner and supported by multimarkdown.
We treat the contents as markdown blocks under a section
header.
Added to documentation and tests.
