Adapt tab concept in title area and control area //card #43

- create and import tabs.scss
- increase base font from 13 to 16px for better readability
- remove link-color from headlines in title area
- this commit fixes rearrangement of header/title area in task https://trello.com/c/RvbGlFAl
add method getStartTimeCode to timecode module
timecode.parse always returns an array
Create header element for headlines and subtitle in title area
Restructure Title Area & Refactor SCSS

- Create & import partials for layout elements 'controlbox' and 'titlebar'
- Delete obsolete browser prefixes in titlebar elements
- Positioning fixes for elements in titlebar
Add class 'flexer' to Titlebar for flexbox layout
Decrease font-weight for headlines, add rules for class 'flexer'
Add autoprefixer to Makefile for postprocessing vendor prefixes in CSS

- update readme file for autoprefixer explanation
Fix layout in titlebar

- add new classes to markup
- add mixins for buttons and icons
- fix position of elements in titlebar
- refactor styles with new mixins
refactor chapter tab to chapter module

The chapter module returns instances of `Chapters` and expects the player and
the player parameters in the constructor.
The chapter module has its own update method that needs to be called whenever
a timeupdate event occurs.
Add method `addEventhandlers` for adding click event handlers for the chapter
table entries.
All methods and functions were refactored for maintainability were possible.

Add method TabRegistry#update that is called on timeupdate of the player.
This is a hook for modules to get updates. Will later be replaced by
Timeline#update.

Add method TabRegistry#addModule that registers the listener as well as
the tab of the module within the TabRegistry.

logCurrentTime function is automatically called upon timeupdate.

The player module now calls tabs.update on timeupdate.
All old chapter handling code is removed or commented out. The chapter
integration is adapted for the chapter module.
One call to window.location was replaced with setFragmentUrl.
Merge branch 'tabs' of github.com:podlove/podlove-web-player into tabs
Fix flex layout in titlebar

- delete flexer class in markup
- write mixins for flexbox layout and  import them by titlebar elements
- neat up layout and elements' positions
Rename classes and refactor styles
Rename class and partial 'controlbar'
Fix layout for controlbar

- write mixins for buttons
- refactor button-styles
Create modules directory plus module scss files
refactor chapters to player module

Almost a rewrite of the chapter update logic. The chapter module knows
its state like the currentChapter and all available chapters in the
playing media file.
The chapter control buttons are working now. Although the example files
are too small/short to show this. Try with a longer media file.
Annoying autoplay is disabled for now, too.

TODOS: fix buffering in chrome, fix issues with ultra-short chapters,
create debug/log modules, separate module logic from rendering
enable tabs to be open on player init

currently implemented for the chapters tab only
First layout fix of tabs

- Delete all gradients and other unused styles from tabs elements
- Replace style 'height:auto' for a fixed height in tab.js
- Comment-out hard-coded css-styles for class 'tab' in chapter.js
- Wrap anchor-elements in controlbar with ul and li elements
- First attempt to create mixin / classes for css-arrow as indicator for state active in tabs
- General make-up of tabs elements according to new layout
Merge branch 'tabs' of https://github.com/podlove/podlove-web-player into tabs

Conflicts:
	js/modules/chapter.js