Fix broken inline CSS parsing and add a iterator for children.

If '\r' appears in an inline <style> element, libhubbub splits the text nodes
there, creating multiple text children. The inline style logic assumed that
each <style> element had only one child.

The logic was moved to trigger when the style element is finished parsing
completely (including the children), and then the children are concatenated
before sending it to the parser.
Bump rust-css.
Remove spurious whitespace.
auto merge of #606 : metajack/servo/broken-inline-css, r=jdm

This add a new children iterator to abstract node and fixes a bug where inline stylesheets got parsed piecewise due to \r style line endings.