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
fix SocialNetwork.getProfileUrl
minor readability improvement in SocialNetwork
fix info module sharing buttons

The implementation is now compatible with SocialNetwork.getButton.
Instead of concatenating strings objects are combined.
add twitter-profile to which-format example
Merge remote-tracking branch 'upstream/dev' into minimal

Conflicts:
	src/js/app.js
	src/js/tabregistry.js
make it all work without chapters ... again

Group module creation and tab registration in app module.
Refactor and improve Chapters constructor. Will return early with null
when timeline has no chapters.
ProgressBar module shows and updates chapter info only when present.
improve minimal and injected example
update version in app module
Merge remote-tracking branch 'upstream/minimal' into social-profiles

Conflicts:
	src/js/social-network.js
fix display of profiles in info tab
add flattr to profile list in which-format example
fix flattr profile url
replace flattr with email in which-format example
Merge pull request #200 from line-o/social-profiles

Social profiles