Twig package for Debian

Packaging rules for Twig template library.

When a new version of Twig is released:

1. Update debian/changelog to reflect changes.
2. If necessary, change $DEBIAN_VERSION in build.sh (only if changing from -1).
3. Run build.sh to download and build the package.
4. Fix any lintian errors/warnings and re-build as necessary.

The build.sh script will create a .source.changes file in /tmp. Upload this to your launchpad PPA with dput ppa:yourname/ppa /tmp/twig_1.XX.X-1~distribution1_source.changes