master: Project-based HTML/CSS class edits

[anythingcodes]

Changes include:

• Using CodePen embeds for a more visual, interactive learning experience (note: CodePens will not work when viewing on file:// URLs -- please publish the slides to GitHub or run them locally)
• Providing students with HTML and CSS cheatsheets at each class
• Working towards a tangible project, which introduces the development workflow and use of Photoshop or other UX tools
• Use of HTML5
• File path review exercise, since this is commonly confusing for beginners
• Use of new slides template for the core curriculum
• Clarification on 'display' and 'position'
• Clarification on box model with practical, visual examples used in project
• Bonus content on publishing a site (not to be reviewed during class, but there if students want to review)

See slides output at http://gdiboston.github.io/gdi-core-html-css

[Roenok]

We'll review this as part of the upcoming curriculum sprint