Update HIE install instructions

[Gipphe]

Recommend ./install.hs build instead of the now removed ./install.hs build-all.

Add section on installing on Windows.

Closes #175

[alanz]

@jneira are you happy with this?

[nponeccop]

I think we should universally recommend enabling per-user Unicode paths for Git. I don't see any downsides. And the Unicode paths is basically using the right API instead of a legacy API. GHC for example already does that. If the right API is used, there are no limits for paths, except for SetCurrentDirectory calls, which (as Microsoft explains that) cannot be modernized because GetCurrentDirectory doesn't work well in multithreaded setting, so making it

Currently it looks like the Git setting and Long Paths setting are interrelated while they are not. The former is fixing a bug in Git while the latter is sort of workaround which breaks behaviour system-wide and it's not always a safe thing to do.

I'm not sure if we should have a separate issue/PR for this - there has been too many Readme-related changes lately.

[jneira]

are you happy with this?

yeah, thanks for updating this @Gipphe