Initial version of a CVE converter to asciidoc

The asciidoc file can be converted to any format supported by
an asciidoc parser. The CVE is fetched via the standard web API
(so it can be used in standalone mode).

You can generate an HTML file from the asciidoc:

python3 cve_doc.py  -c CVE-2015-0003 | asciidoctor - >test.html