Fixed syntax error in crowbar.yml

'@' is a reserved character in YAML, and needs to be quoted:

    http://yaml.org/spec/current.html#id2515596

otherwise rubygem-psych (as in ruby 1.9) complains about it and causes
barclamp_install.rb to exit.
Merge pull request #110 from aspiers/pull-req-master-9d9e0e065e56866b3d17ffa42bb595796a133c2a

Merged by devtool for cloudedge