add minimal example
enable playback with minimal data

* in app module: add eventhandlers to chapters only when present
* fix function normalizeSource in downloads module
* info module and tab is skipped completely when summary is missing
* TabRegistry.add can cope with null values
* Timeline instances work without chapters
Chapter hot fix

- Delete rendering of an external link next to the chapter name
- Delete unused debug log
- Comment-out chapter image column and delete its styles
(we’ll need it later for ‘unfold chapter summary’ feature and will
rename it then)
- Delete styling of chapter image column
- Add behavior of active and inactive chapter duration color
WIP re-enable video playback
New variable for icon font-size

on screens smaller than 480px
Mixin iconfont-button: Replace text-shadow for opacity

Leave the light text-shadow effect only on open, therefore active tab
icon.
Responsive layout for control-buttons #1

First solution: Display both lists in a row on wide screen, in two rows
on smaller screens.
Create container for timecontrolbar
Create container for toggle bar
Styles for timecontrol bar and toggle bar wrappers
re-enable video playback

* remove old mediaelement.js styles since we only use its API
* add _video.scss for styling the current video element
* rename `.podlovewebplayer_top` to `.video-pane`
* refactor event play button creation and event listeners in app module
* reuse play button for video playback

fixes https://trello.com/c/Bd0eeOgd/78-fix-video-player
add poster image to video example
Merge pull request #202 from podlove/fix-video

Fix video
Change markup for toggle bar and control bar #2

- Append toggle bar to wrapper element instead of controlBox.
- Both lists are nested within a wrapping container now.
- Both wrappers have a new class ‘bar’ for general bar-styling, that
will be extended by class ‘togglebar’ and ‘controlbar’.
Create class 'bar' to define general styling for controls

Import file _controls.scss to main scss file.
Styling for control bars 'togglebar' and 'controlbar'.

Responsive behavior already included!
use registered bower package for podlove font
Merge remote-tracking branch 'upstream/controlbar-changes' into dev

Mediaelement was deleted and togglebar added at the same line.

Conflicts:
	src/sass/podlove-web-player.scss
minor fixup
fix playButton click handler