Link WSK Extras repository from the main readme file.

Fix for #365
Merge pull request #369 from crhym3/extras-repo-link

Link WSK Extras repository from the main readme file.
Simplified overview section of readme
Merge pull request #371 from Garbee/overview

Simplified overview section of readme
Update .jscsrc

update indent value of .jscsrc file and follow style rule.
Merge pull request #374 from antleblanc/master

Update .jscsrc
Fixes #375: sync recommendations (index > basic)
Improve index.html comments.
Moving styleguide around
Renaming CSS files to .scss and dropping components.css
Fixing up the html files to no longer require useref for CSS
Fixing up the styleguide to work correctly with the sass stylesheet
Fixed the gulp and gulp:serve tasks to work
Merge pull request #377 from google/comments

Improve index.html comments. Fix #360
Adding the comments from master into the branch
Rebase against master.
Merge pull request #379 from google/styles-rework

Restructure our Styles.
add spacing to css selector
Merge pull request #381 from antleblanc/master

add spacing to css selector
Add `box-sizing` as an inherited value

This way, it should be easier to modify it's value for vendor components that don't handle `border-box` properly. For further details check: http://goo.gl/DGLMbk.