build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Improve README.md

Refs: #5095
Change-Id: I0972967e92bdf78b8ab7cda0d9db262e38c8b32b
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 # NDN Certificate Management Protocol (NDNCERT)
 
+![Language](https://img.shields.io/badge/C%2B%2B-14-blue.svg)
 [![Build Status](https://travis-ci.org/named-data/ndncert.svg?branch=master)](https://travis-ci.org/named-data/ndncert)
 
-NDN certificate management protocol (NDNCERT) enables automatic certificate management in
-NDN. In Named Data Networking (NDN), every entity should have corresponding identity
-(namespace) and the corresponding certificate for this namespace. Moreover, entities need
-simple mechanisms to manage sub-identities and their certificates. NDNCERT provides flexible
-mechanisms to request certificate from a certificate authority(CA) and, as soon as certificate
-is obtained, mechanisms to issue and manage certificates in the designated namespace. Note that
-NDNCERT does not impose any specific trust model or trust anchors.  While the primary use case
-of the developed protocol is to manage NDN testbed certificates, it can be used with any other
-set of global and local trust anchors.
+The NDN certificate management protocol (**NDNCERT**) enables automatic certificate management
+in NDN. In Named Data Networking (NDN), every entity should have a corresponding identity
+(namespace) and the corresponding certificate for this namespace. Moreover, entities need simple
+mechanisms to manage sub-identities and their certificates. NDNCERT provides flexible mechanisms
+to request certificates from a certificate authority (CA) and, as soon as the certificate is
+obtained, mechanisms to issue and manage certificates in the designated namespace. Note that
+NDNCERT does not impose any specific trust model or trust anchors. While the primary use case of
+this protocol is to manage NDN testbed certificates, it can be used with any other set of global
+and local trust anchors.
 
-This specification provides details and packet formats to request certificates, create
-certificates after one of the validation mechanism, and how the issued certificate is retrieved
-by the original requester.
+See [our GitHub wiki](https://github.com/named-data/ndncert/wiki) for more details.
 
-See [our GitHub wiki](https://github.com/named-data/ndncert/wiki/NDN-Certificate-Management-Protocol)
-for more details.
+## Reporting bugs
+
+Please submit any bug reports or feature requests to the
+[NDNCERT issue tracker](https://redmine.named-data.net/projects/ndncert/issues).
+
+## Contributing
+
+We greatly appreciate contributions to the NDNCERT code base, provided that they are
+licensed under the GPL 3.0+ or a compatible license (see below).
+If you are new to the NDN software community, please read the
+[Contributor's Guide](https://github.com/named-data/.github/blob/master/CONTRIBUTING.md)
+to get started.
+
+## License
+
+NDNCERT is an open source project licensed under the GPL version 3.
+See [`COPYING.md`](COPYING.md) for more information.