Compatability with marked 0.2.10 and docco 0.6.3.

The `<h1>` tags in `marked` version 0.2.10 contain the `id` attributes
which we were manually adding in the grunt `addHeaderIds` function,
causing the match in `parseMarkdownOutput` to fail (and grunt to
crash).  Allow `<h1>` tags to contain (simple) attributes.

In `docco` version 0.6.3, the `docco.parse` function added an optional
`config` parameter, but docco crashes if you use the default value.
Filed and patched upstream in https://github.com/jashkenas/docco/pull/291
but work around this for now by passing `{languages:{}}` as the third
parameter (which is safely ignored in docco 0.6.2).