README - remove probably useless part of Docker installation instructions

Signed-off-by: Pang Yan Han <yanhan@viki.com>
README - update git clone url

Signed-off-by: Pang Yan Han <yanhan@viki.com>
README - clarify that software must be installed for Storm cluster machines

Signed-off-by: Pang Yan Han <yanhan@viki.com>
README - state that `Configuration` instructions are for all Storm machines

Signed-off-by: Pang Yan Han <yanhan@viki.com>
README - add assumption about configuration files

Signed-off-by: Pang Yan Han <yanhan@viki.com>