Viewer and summary page prettification (#851).

- Compact navigation controls in viewer chrome.
- Move share button to header, compact a bit.
- Include basic story detail on summary page, style a bit.
- Open issues:
  - Viewer chrome logo *not* working in this commit.
  - Summary page TOC links not working in iframe mode.
  - The share button is added by the viewer; iframe-mode controls
    (close, open in new window) are added by the detail page. To
    avoid messy attempts to align these, and because semantically
    they are quite different groups of controls, the share button
    lives in the bottom of the header rather than next to the
    "window-level" controls.
  - To avoid conflict I did not upgrade this branch's version of
    Font Awesome. The "open in new window" icon is therefore not
    the "icon-desktop" as recommended in #851. I'm not 100% convinced
    that that's the right icon, anyway.
Fix logo and summary TOC behavior (#851).

- Make any list with .story-toc class eligible to trigger nav events.
- But also *only* toggle open/closed the TOC in viewer chrome. :)
- Logo for viewer, styling to match.
- Note: NOT tested in IE8.
Merge branch '851-viewer-summary-improvements' of https://github.com/patternleaf/atlas into patternleaf-851-viewer-summary-improvements

Conflicts:
	apps/storybase_story/templates/storybase_story/story_viewer.html
	static/css/style.css
	static/less/viewer.less

Conflicts were due to the moving of the share button to the header and
the use of the old ``storybase-share-widget`` class for the button
instead of the ``storybase-share-button`` class introduced as part of
the implementation for #824.
Add link to story detail page from viewer

Add a link to the story detail page in the header of the story viewer.
This is particularly important for when the viewer is shown in a popup
from a widget.

Give the share link the class ``storybase-share-link`` so we don't
have to override the ``storybase-share-button`` styles and so it's
easier to match the styles of the other links in the ``#tools``
container.

Addresses #851
Fix summary layout on smaller displays

With a 50% column width, the table of contents overlapped the image.
Make the column with 48% to prevent this.

Tall featured images were also pushing the summary text outside of view.
Move the summary text to the top of the display, pushing the table of
contents down.

Add padding to the bottom or elements so they don't get cut off by
the footer.

Remove the byline as it's redundant with the omnipresent header bar.

Addresses #851
Also add footer-clearing padding to image container

Addresses #851
Use CSS IDs instead of classes for summary elements

The elements are unique to page, so an ID seems more appropriate.

Addresses #851
Clean-up summary updates in spider story

The summary element gets moved into a dynamically created
sidebar element. Needed to change the selectors in the Backbone views
to match the new styling. Also change the viewer template to have
different markup for spider and linear structured stories.

Addresses #851
Merge branch 'patternleaf-851-viewer-summary-improvements' into develop