Updated version to 0.15
NPM requires x.x.x style version number
Fixes #172 ARIA landmarks
Added main landmark to epub content region.
Changed toolbar region landmark to banner from navigation
Added a region named Page Navigation to prev/next button area
Added Page Navigation to EN-US messages.json
Added empty alt attribute to empty library arrow image
Merge pull request #176 from becka11y/feature/landmarks172

Fixes #172 ARIA landmarks
Fixes #177 Settings Dialog ARIA issues
Added aria-label to dialog element rather than aria-labelledby
Changed invalid role of buttongroup to group on Text and
Background color grouping element
Still some JAWS and VoiceOver screen reader issues
but NVDA works correctly and as expected
Merge pull request #178 from becka11y/feature/settings177

Fixes #177 Settings Dialog ARIA issues
Removed ability to load a url in the chrome extension
Merge branch 'develop' of https://github.com/readium/readium-js-viewer into develop
Split apart @larsvoigt's work that adds support for next/previous button visibility toggling
Merge pull request #180 from readium/feature/prev-next-button-visibility-lars

Split apart @larsvoigt's work that adds support for next/previous button visibility toggling
Submodule update to fix #181
update submodule
update
Merge branch 'develop' of https://github.com/readium/readium-js-viewer into develop