Release 2.0.0

[levimcg]

Release PR for next major version of the Rivet icon set.

@basham I've updated the README and bumped the version number in package.json. I think I got all of the 1.x references updated, but you might want to double-check and make sure.

• Updated the View Demo URL in the README
• Updated script and style references to version 2
• Removed reference to old .ai file
• Removed gh-pages deployment instructions
• Bumped package.json version to 2.0.0

Once approved I can merge, release the npm package, and create a new GitHub release.

[levimcg]

@basham Oh, also. Once we finish the release, I'll update the URL in the about section of the repo home page and then delete the gh-pages branch.