Add setup instructions for mac and linux.

[ketan-survival]

See our contributing guides.

Script will fail if required utilities such as npm and wget are not present on the system.

Presently, the script will carry on with the rest of the commands but it should halt if any of the previous commands fail.

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(update by @octopusinvitro)

What to do:

Update the README section "To initialise the project" right after the title to indicate that wget and npm and ruby need to be installed to use the application. Provide helpful links, for example:

• wget: mac | ubuntu
• npm: node version manager | node and npm
• ruby: rbenv manager