Merge commit 3f98f13 'Export `parse_color_keyword`' into to_css
Refactor ToCss to use TextWriter.

https://github.com/SimonSapin/rust-std-candidates#the-textwriter-trait
Implement ToCss for more AST things.
Implement ToCss for Color and RGBA
Add ToCss::fmt_to_css, a convenience method for implementing Show.
Implement ToCss for declaration lists
Add CssStringWriter
Merge branch 'to_css'

Conflicts:
	Cargo.toml
	src/color.rs
	src/serializer.rs
Upgrade to rustc 0.13.0-nightly (99d6956c3 2014-12-18 20:32:07 +0000)
Merge pull request #67 from servo/to_css-merged

Modernize the ToCss trait and implement it on more things.