Remove grids-r.css

We'll be using [rework-pure-grids][1] to generate responsive
grids on a per-app basis. This is more useful than having
.pure-g-r inside Pure's `src/` since media queries cannot
be over-written.

[1]: https://github.com/ericf/rework-pure-grids
add .img-responsive class to base.css
remove .pure-g-r from forms manual test
Update dev dependencies
Remove transitions from Buttons and Forms

Fixes #273
Reduce padding/add room on color input for Chrome (v32/34 OS X).
add “main” to bower.json
Update copyright to 2014
Update grunt-contrib-compress dependency and swich to release tarballs

To resolve file mode issues with the .zip release files, this switches
to using tarballs instead.
Separate out `:not()` selectors from CSS 2.1 selectors.

IE8 won't execute the CSS block if it contains a CSS3 selector.
This makes IE8 still execute the CSS, and CSS3-compliant browsers
can support the `:not()`.
wrap comments at 80 chars
fix dangling brace
Merge pull request #290 from tilomitra/261-fix

Separate out `:not()` selectors from CSS 2.1 selectors.
Update and tweak HISTORY.md
Bump version to v0.4.0
Bump version to PRE
Downgrade grunt-contrib-cssmin to v0.6.x which uses clean-css v1.x

grunt-conrib-cssmin v0.7.x uses clean-css v2.x which adds "advanced"
options which totally borked the Pure v0.4.0 release.

**Note to self:** If I ever write a trivial Grunt plugin that wraps some
dependency, tie their version releases to the same slot, e.g. bump the
major version number if the dependency's major version number changes.
Update HISTORY and README for 0.4.1, the new 0.4.0
added config
Bump version to v0.4.1