Issue #37: Lorax would fail if old artificats existed

This fixes issues when rebuilding without clearing out tmp/. We still
need a decision on when to clear out the build directory. For example,
the x86_64.log will be appended to after each build. Also, some LiveOS
directories remain after mksquashfs is called. This will be addressed in
issue #79.
Issue #37: Bump Lorax version