Add Bower install and more to README

* Mention v1's support for legacy browsers.
* Provide link to project page for easy download.
* Include Bower install command.
Clean up component.json

Bower doesn't currently use several properties that were included.
Keep `styles` for now, for Component(1).
Protect root against system color schemes

System color schemes (in particular, custom themes in Windows and Linux
distros) affect Firefox, IE, and Opera. Normalizing the web site/app's
root background and text color prevents these unwanted settings from
being used. Chrome doesn't apply system-level schemes to websites.

Fix gh-170
Fix typo
Change gh-page URLs to use `.io`

GitHub have redirected all `username.github.com` pages to
`username.github.io`.
Add contribution guidelines

Includes process for maintainers while there is no automation in place.

Close gh-175
Fix example `git tag` command in docs
v2.1.1
Fix typo in CONTRIBUTING.md
Correct date of 2.1.1 release in CHANGELOG
Change the Bower website URL
Add Bower manifest file

Ignore files that don't need to be installed.
Simplify the Component(1) manifest file
Revert root color and background normalization

Commit: 907890983eb2d6667e4b9cbd8bd03ead4b077e34

The change caused problems with `body` background color no longer
bubbling up the the `html` element.

It also prevented you from setting `color` or `background` styles on
`html` before the normalize.css styles.

It might not be possibly to safely address – within normalize.css –
the problem that it was trying to avoid.

Fix gh-188
Add `bower.json` to release instructions
v2.1.2