Initial crack at #518: story viewer should be navigable such that one section is shown at a time.
Story viewer: hide toc on click on story section. (#518)
Story viewer: substitute "Section x" when section titles are blank. (#518)
Story viewer: highlight current entry in toc. (#518)
Story viewer: refine open/close behavior. Click outside of toc closes toc. (#518)
Story viewer: tweak usability of TOC. Link target area takes up full width. Hover state indicates that. (#518)
Remove PublishTodoView

Since agreeing to the legal requirements is no longer required, and
stories are given a default creative commons license, there's no need to
have the overhead of keeping track of which steps of the publish flow have
been completed.

Addresses #515
Viewer: make prev/next buttons stay put and enable/disable rather than appear/disappear. Tweak styling. Add a (x/x) section counter below prev/next buttons. Note: in this commit the title attribute on the prev/next buttons is not present because handlebars is totally kicking my butt with some behavior that seems really strange to me but is probably down to a misunderstanding of either how it works or the structure of context data being passed in. (#518)
viewer: fix for missing title attributes on previous/next buttons. Unclear on reasons why this is necessary. (#518)
Viewer: tweak hover styling on previous/next buttons. (#518)
Viewer: tweak for prev/next button visual state on disabled and hover. (#518)
Removed unused SectionNavView
Catch timeout to CC API

Catch timeouts and other errors when making requests to the upstream
Creative Commons license API via our proxy.  Also, cache the responses
for 24 hours so we're not making so many requests and so the respons time
is faster.

Closes #605.
Update story slug when the story is published

Closes #596
Update changelog preparing for 0.5 release
Only set asset licenses when story has been saved

Without this check, the initial save of a story in the Django Admin was
failing.
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 'develop' of https://github.com/PitonFoundation/atlas into 518-story-viewer-nav