The most basic possible scheme for implmenting .htaccess style http authentication.

This simply checks the containing directory of each request for a .htaccess
file.  If one is found, it "hot swaps" in a basic_auth instance to the
containing path.  This has the effect of immediately requiring the
username/password specified statically in tangelo.py itself (alice/scatter).

To make this really work, the server needs to keep a dict mapping paths to the
info found in that path's .htaccess file.  We need to think about things like,
do we want to track the mtime of the .htaccess files for the purpose of keeping
the server's dict up-to-date, etc.  A first attempt won't worry about that, but
will simply allow people to keep their applications relatively secure.
Abstracted htaccess file parsing/etc. from path handling function.
Restructured logic for handling htaccess file.
Adding dummy class for parsing htaccess file.
Digest authentication works.  Need better logic to account for presence of .htaccess files in ancestor directories.
Improved http auth logic - now checks all ancestor directories for .htaccess files.

Http auth seems to be working correctly now, but needs to be tested.
Added directory listing ability.
Ignore empty lines in .htaccess files.
Using argparse for tangelo script's command line arguments.
Merge branch 'httpauth'