Fix fieldset width in Chrome and Firefox

Fixes an issue in Firefox [1] and Chrome [2]. The implicit width of
`fieldset` can be determined by the width of descendants rather than the
parent container. This change (adding `min-width:0`) makes the
`fieldset` behave like a `div` in this regard.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=504622
[2] http://stackoverflow.com/questions/8084343/google-chrome-fieldset-overflow-bug

Close #272
Fix `font` and `color` inheritance for forms

Inherit all `font` properties.

Inherit `color` for form controls. Chrome and Safari on OS X will not
inherit `color` as they heavily restrict the author-defined styles that
will be respected for that element.

Fix gh-157
Set correct display for `progress` in IE 8/9

Set to `inline-block` to match default value in modern browsers.

Fix #253
Close #254
Remove default table cell padding

Normalize.css makes some convenience changes to the default table
rendering. This change removes the 1px of padding around table cells.
Normalize `optgroup`

Address Firefox not inheriting `font` properties for `optgroup`.

Fix gh-102
Fix `optgroup` normalization and add test

Ref gh-102
Fix `figure` margin normalization

All browsers that support `figure` apply margin of `1em 40px`.

Fix gh-262
Remove `a:focus` outline normalization

My hypothesis is that it's more important for a user to get the focus
style they expect *within* their browser than it is to have consistent focus
styles *between* browsers. In particular, replacing Chrome's default focus
style (esp. just for links) seems presumptuous.

Component designers/developers can make the decision on when to modify
these browser defaults.

Fix gh-216
Automatically rewritten for npm.