Add .jshintrc with common jQuery code guidelines options

Also tell jshint grunt task about it.
Fix: remove extra var statements in app.js

Use commas between variables, use one "var".
Add jQuery to .jshintrc
Fix: remove extra var statements in story.js

Use commas between variables, use one "var".
Don't specify "window" namespace when define new module
Fix: remove extra var statements in header.js

Use commas between variables, use one "var".
Fix var statements in story.js
Add localStorage to globals in .jshintrc
Fix variable declaration in story.js: make it local
Fix var statements in story.js
Fix var statements in app.js
Fix whitespaces in app.js
Fix jshint's W117 (variable is not defined): add global story
Fix var statements in header.js
Fix jshint's W117 in init.js: add global app
Fix jshint's W117 in on-off-button.js: add global app
Allow multiple "var" in story.render

That's because there's if-else with variables needed only inside
one block.
Don't know what about performance, but this sure adds readability.
Add "use strict" everywhere
Merge branch 'develop'