Include Open Sans Bold web font in dartlang.org pages

[DartBot]

This issue was originally filed by sander.dijkhu...@gmail.com

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The pages on dartlang.org use this tag to load Open Sans:

<link href='http://fonts.googleapis.com/css?family=Open+Sans' rel='stylesheet' type='text/css'>

This doesn't load the boldface file, while some parts like .intro > dl > dt are set in boldface. Currently this means that the regular font is made bold programmatically at these places, which looks very bad.

Instead, please use this tag:

<link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700' rel='stylesheet' type='text/css'>

[DartBot]

This comment was originally written by drfibonacci@google.com

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Done, will show up in next push

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Set owner to drfibonacci@google.com.
Added Component-Docs, Fixed labels.