Make readme more fool-proof

[hugomflavio]

I was trying to follow the instructions on the readme but got stuck at line 24 and onward. I installed freeciv21 and located the /usr/local/share/freeciv21 folder, but I am not sure what 'the local setup above' in line 24 is referring to?

I have also noticed that I do not have a ~/.bashrc file. In this case, should I just create a new one, or does that mean I am doing something wrong? I ran subl ~/.bashrc (just because I usually edit text files in sublime).

If not having a ~/.bashrc is normal, perhaps we should change the wording a bit in these lines? When I see 'add something like this to the bottom' in line 27, it makes me think I should be editing a previously existing file.