restructure: refactor 2 modal dialog services
share-social: disable fb share button for now
share-social: fb button only on game page
share-social: fb button only on game page
Merge branch 'share-social' of github.com:xuanluong/15-puzzle into share-social
Merge share-social
layout: update explanation part to be mor succinct
layout: add Sass
layout: refactor css using Sass
layout: refacter css (cont.)
layout: complete refactor css with Sass
gh-pages: revert to temporary mobile friendly mode
layout: convert to rem unit
layout: define different font-size for different screen sizes
Accommodate larger screens on handheld devices
layout: redefine header layout
Merge branch 'master' into layout

Conflicts:
	build/css/15-puzzle.css
	build/css/15-puzzle.min.css
	src/css/style.css
	src/css/style.scss
layout: improve scaling for screen sizes
share-social: align facebook share button
share-social: align Twitter share button on iPhone