Session 4/5/6 Combined Pull

Accidentally wiped Session 4 branch before it could be merged on remote, but changes have been rolled forward into Session 5 branch.  New updates include Session 5 labs for testing, comprehension, and argument passing.
don't need the lambda -- str.strip is already a function:

map(str.strip, fid)

also note that a file object is an iterator, so you can just pass the file object in to the map(), without the readlines() call.