unpack_and_config works now in testing

- Changed the formatting of the example script call, HERE documents honor
  single backslashes... who knew? :/
- Used /usr/bin/basename to get the filename of the tarball, so that you could
  later in determine the name of the source directory ($SOURCE_DIR) once the
  tarball is unpacked
- Added tar handlers for different tarball types (.gz/.xz/.bz2)
- Use an eval on the actual tar command so things like tildes expand
- Don't run ./configure in a subshell, always show it's output
- Show the ./configure command that will be run before running it