Use linear rather than exponential time algo for finding transitive deps

in tools.namespace.  Filed ticket TNS-18:

    http://dev.clojure.org/jira/browse/TNS-18

It seems likely that a different change will be some day made to
tools.namespace than this.  Read it over if/when it is made, and
decide what to use going forward after that.
Update list of changes made to copieddeps after copying them in.