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Deleted the debian/copyright file because it was outdated; I think this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.

Fix two bugs:

 - nvdjson.smartVerCmp was comparing the full version strings instead of
   major, minor, path etc. substrings;
 - off-by-one error in AttributeColumnMap.CPE()

Fixing versioning of releases to get rid of `v` in files (facebookinc…

…ubator#20)

* Fixing versioning of releases to get rid of `v` in files

Current releases had `v` in all the files which is against a current standard.
Therefore, we should remove this.

* Changing tarball non-standard binary names

Solving issue facebookincubator#19 to make tarballs contain standard binary names and removing the redundant /binaries directory

Test:
build the tarbals with `./build_tarballs.sh`
and checked the tarball contents:
```
vagrant@ubuntu-xenial:~/repos/nvdtools/release$ tar zvft nvdtools-4.4.4-linux-amd64.tar.gz
-rwxrwxr-x vagrant/vagrant 3513959 2019-01-24 00:36 cpe2cve
-rwxrwxr-x vagrant/vagrant 2233700 2019-01-24 00:36 csv2cpe
-rwxrwxr-x vagrant/vagrant 8595732 2019-01-24 00:36 nvdsync
-rwxrwxr-x vagrant/vagrant 2229430 2019-01-24 00:36 rpm2cpe
```

update github oauth token