support for dip links in progress
fixing internal links navigation
exposing iframe events subscription api
fixed bug on missing function for fixed layout
Merge branch 'develop' into feature/deep_link_cfi_resolve

Conflicts:
	js/views/fixed_view.js
restorred addIFrameListener function
Media Overlays highlighting, custom styles from reader / user. fixed minor SMIL parsing issue
ah, reader method was missing (lost in recent merge? not sure...)
MO element visibility cleaned-up (optimised, by using first 100% visible item, of previous partially-visible item)
fixed minor MO bug: playback status was out of sync in edge-case of embedded video/audio sync
fixed jQuery selector issue (escape special characters), was affecting Media Overlays playback (not sure about other functionality)
Unifying visibility check (always returns a visibility percentage)
Merge develop branch, minor fixes