OEC 360, no duplicate rows in oec:courses output

We get duplicate rows in final resultset due to post-processing of 'cross_listed_name' column (i.e., cross-listed CCNs can be reported twice). The easiest "fix" is to ignore dupes during generation of courses.csv. Overhauling the code (SQL, etc.) is unnecessary.
@christianv  Good catch. That was inadvertent. My local run of 'rvm rvmrc' was not right.  Fixing