Add embeds and fix broken links

[samrobbins85]

Changes proposed:

• Add codepen embeds in the documentation for easier understanding
• Fix a few broken links in the documentation

Acceptance Checklist:

• The commit message follows the guidelines in CONTRIBUTING.md.
• Documentation (README.md) and examples have been updated as needed.
• If this is a code change, a spec testing the functionality has been added.
• If the commit message has [changed] or [removed], there is an upgrade path above.

[coveralls]

Coverage remained the same at 87.135% when pulling b6c2c24 on samrobbins85:master into bd07d56 on reactjs:master.