README.md: Fixed Python Kafka library name and added libssl development
README.md: Fixed Python Kafka library name and added libssl development

The name of the Python Kafka library was mispelled. It should have been
kafka-python rather than python-kafka. And besides libffi-dev/-devel
libssh-dev/-devel is required.

Signed-off-by: Rudolf J Streif <ea7b312ba06c558b2c165670d6c670057f7928aa@gmail.com>

klooer/rvi_backend,dvthiriez/rvi_backend,PDXostc/rvi_backend,klooer/rvi_backend,dvthiriez/rvi_backend,PDXostc/rvi_backend,klooer/rvi_backend,rstreif/rvi_backend,rstreif/rvi_backend,rstreif/rvi_backend,dvthiriez/rvi_backend,rstreif/rvi_backend,PDXostc/rvi_backend,dvthiriez/rvi_backend,PDXostc/rvi_backend,klooer/rvi_backend