Replace advice of using vim for Sublime Text.

This is considerably easier to use for non cli-savvy users.

Fixes #493
Include link to latest web-starter-kit release.
Update provide-real-time-validation.markdown

Changed IP Address validation into three different validations: IPv4, IPv6 and IPv4 + IPv6.
Adds Node and Grunt dependencies to README.
Adds Gemfile and Gemfile.lock and updates README.

Conflicts:
	README.md
Merge branch 'master' into adds-gemfile

Conflicts:
	src/README.md
Fixed spelling mistake
Merge pull request #517 from dowsieboi/spelling_mistake_fix

Fixed spelling mistake
Merge pull request #515 from jbnicolai/adds-gemfile

Adds Gemfile
Merge pull request #510 from jbnicolai/replace-vim-for-sublime

Replace vim for sublime
Merge pull request #509 from jbnicolai/link-latest-wsk-release

Include link to latest web-starter-kit release.
Fixes #497 - removes reference to cygwin
Merge branch 'master' of github.com:google/WebFundamentals
Merge pull request #511 from ikkebr/patch-1

Update provide-real-time-validation.markdown
Fixes #521 - updating the location of the images
Merge branch 'master' of github.com:google/WebFundamentals