Render border solid-style properly
Add diamond test code
Modify indents
Update submodule
auto merge of #1276 : hyunjunekim/servo/RenderBorder, r=pcwalton

Implemented a border which was the solid type.
Because of not support css pseudo element(:before, :after), content in css property and base64, So we couldn't test Acid2(http://www.webstandards.org/files/acid2/test.html).