First pass at #530: character count indicator and limit warning in builder.
Builder summary: poll the editor to update character counts. There is currently no change event on the editor that fires when we want it to. Polling is a hopefully temporary stop-gap. (#530)
Update readme for issue #530.
Merge branch '530-summary-word-count' of https://github.com/patternleaf/atlas into patternleaf-530-summary-word-count

Fix merge conflict in README.rst and re-ordered changelog entries so
they're ordered by version number.

Conflicts:
	README.rst