Add packages dir back to repo

Meteorite used the packages directory to store links to all the
dependencies -- so gitignoring it was prudent to avoid sharing broken
symlinks.

But Meteor >v0.9 uses it to store local code that is packaged.  In
particular, we need npm-container to be there to avoid crazy dances when
bundling. It should be safe to not .gitignore it and add all its
contents now.