Enable xvfb for Specs on Travis

Include webkit-capybara enabled specs in travis run.
open page by param with its own sharing meta infos
add up to 3 image urls in meta tags for sharing
add 'social' tab and share image to editor
move some code to social share helper/namespace
add helper to force protocol of urls to http
prevent rendering 404 if no share image was set
add sub-share widget
don't use mouseleave handler on mobile devices
bind touch events on menu items only once
styling for sub share
re-enable share on mobile devices and clean up a bit
cleanup
sub sharing fixes, styling fix for progress bar
Some Wording Changes for Inline Help
Read emphasize_chapter_beginning from Entry Configuration
further fixes for subsharing
Merge pull request #206 from tf/optimize-sharing

Optimize Sharing
Merge pull request #209 from tf/emph-chapter-fix

Read emphasize_chapter_beginning from Entry Configuration
Merge pull request #210 from tf/inline-help-wording

Some Wording Changes for Inline Help