add test in Makefile; add module class
add code class
introduce built-in function compile
add CConstructModule; implement __import__
comment out the pprint statement
merge brownplt/master into modules-rewrite
refine the CConstructModule case in python-interp, which now can raise the exceptions when interpreting module code; revise code style in util.rkt; add test cases for raising exception when importing files;
Merge branch 'modules-rewrite', remote-tracking branch 'origin'
clean testing files