Improvements in the README.rst

[sanchit48]

• This is the official documentation for coala, and it is online at https://docs.coala.io. The coala repository can be found here.

It should be kept clear that the Documentation is in the coala repository. So the line should be
something like The documentation resides in the coala repository which can be found here

• pip3 install -r requirements.txt

This command should be executed inside the coala folder, so, before this command, cd coala command should be added to make things more clear.

[xurror]

I would like to work on this issue if it's not a newcomer issue

[kushthedude]

@KVGarg A New Comers Issue ,

[espatatis]

I'd like to get this issue assigned.