OEC-500, command line options specify source and destination directories

https://jira.ets.berkeley.edu/jira/browse/OEC-500

With respect to OEC rake tasks, Ops (Felder) wants control over source and destination dirs. For example, when running 'rake oec:students' you can specify where courses.csv lives without altering yml file. Furthermore,  results can be written to a tmp dir or the more official svn directory structure that Ops maintains. In this case, Jonathan's preference matters because he's the only one that will run these tasks in production. He is the customer.

Usage:
* rake oec:courses [dest=/export/path/]
* rake oec:students [src=/path/to/source/] [dest=/export/path/]
* rake oec:diff dept_name=FOO_DEPT  [src=/path/to/source/] [dest=/export/path/]

When 'src' and/or 'dest' args are not supplied the rake tasks default to user's working directory (Dir.pwd).