Add more details to INSTALL.md
Add more details to INSTALL.md

Signed-off-by: Vivek Rai <4b8b65dd320e6035df8e26fe45ee3876d9e0f96b@gmail.com>

philippbayer/snpr,openSNP/snpr,philippbayer/snpr,philippbayer/snpr,philippbayer/snpr,openSNP/snpr,openSNP/snpr,openSNP/snpr