'Extracts a zip file into `base_path`'

@classmethod
def extract_zip(cls, filename, base_path='.', verbose=False):

    base_path = cls.abspath(base_path)
    output = (lambda x: (verbose and sys.stdout.write(('%s\n' % x))))
    cls.pushd(base_path)
    zfile = zipfile.ZipFile(filename)
    output(('Extracting    files    to    %s' % base_path))
    for file_name in zfile.namelist():
        try:
            output(('        ->    Unpacking    %s' % file_name))
            f = cls.open_raw(file_name, 'w')
            f.write(zfile.read(file_name))
            f.close()
        except IOError:
            output(('--->    Creating    directory    %s' % file_name))
            cls.mkdir(file_name)
    cls.popd()
