#535 replace @key with @ref for the <resp> example

[Peter Stadler]

At present the example reads

<resp key="com">compiler</resp>

I propose to get rid of the @key attribute and rather use the linked data approach:

<resp ref="http://id.loc.gov/vocabulary/relators/com.html">compiler</resp>

[James Cummings]

F2F Raleigh: 2014-11-19 In general Council has already decided it prefers @ref over @key; Make GREEN; Change example; Reporting back if there are any problems.

[Peter Stadler]

implemented by [r13074]