compiler.py gives away the "remove complex operands" exercise answers

[nrwahl2]

The methods are all stubs through 1441b56. 587bd8f and 8bdbcb3 fill out all the remove_complex_operands code.

Was this meant to go in an instructor solutions repo?

[AndrewTolmach]

Indeed, I think this an accidental leak. (Cover your eyes!)