Refactor: make base.hideOriginal more readable

Structure it, get story rendering as a callback from base.start.
Parse story title in story.parse
Render story title in story.render
Fix story.parse to meet code conventions

- Change $storyId element from ".text" to "[id^=story_]", because it's
the same element, this way it looks more clear that we're dealing with id.
- Add whitespaces where needed.
Add base.css file, move .overlay styles to it
Refactor: restructure code in base.hideOriginal
Move .page-wrap styles to base.css
Move .page styles to base.css
Fix: change "800" to "800px" in base.css
Rename common.js to init.js
Add pubsub.js with pub/sub implementation

Use hash table (plain object) as event list storage and jQuery.Callbacks
under the hood.
Rename base.js to init.js

Also rename window.base to window.init.
Add app.checkEnabled

Start app only if it is enabled (user may disable it).
App gets enabled on first run automatically.
Use localStorage as storage (localStorage.itdelivers key).
Add private method app.setAppEnabled

Also internally rename app.checkEnabled to app.getAppEnabled, but
leave public name the same (app.checkEnabled).
Remove web_accessible_resources from manifest

No need in web (page js scope) accessibility, because code is run in
extension's scope and there're no injections to page.
Moreover, this helps to prevent unwanted injections.
Merge branch 'feature-browser-support-chrome' into develop
Add usage examples to pubsub.js
Add app.showOnOff

Actual private method has name app.renderOnOffButton.
Do the following in this function:
- create div.on-off-button
- set click handler: switch app on/off
- append it to body

Make public alias showOnOff.
Call app.showOnOff in init.js

Call it before checking whether app is enabled, so the button will
always be shown.
Style up on-off button, place styles in base.css