v0.1.3: Update build and release systems

This diff removes the build_tarballs.sh and the rpm/Makefile files and
moves their logic into the main Makefile.

The build system places binary files in the build directory. The release
system copy those files over to the release directory, preparing it for
travis to pick up.

Examples:

make binary_deb binary_rpm VERSION=1.0
make clean binary_tar VERSION=1.0 GOOS=linux GOARCH=amd64
make distclean release VERSION=1.0

Deleted the debian/copyright file because it was outdated; I think this
could be automated with debmake but didn't spend time on it.

There's other minor changes like removing trailing space from files,
updating and adding documentation.

Re-add copyright notice to vulndb/schema.go.