Update deps and a simpler build process

[gaetanlhf]

This small PR offers:

• Upgrading of dependencies,
• A simpler build process thanks to a revised Makefile,
• And of course an updated README.md, linked to the Makefile modification.

What do you think about this?

[akhenakh]

Nice work. Thanks.

I have a working branch around to use the xapian indexes from the zim files.

I'll check if it's compatible with those changes especially around cgo since a c++ binding is involved.

[gaetanlhf]

Well, it's a good idea to reuse the indexes already present in the Zim files. :)
I guess you won't be using Bleve anymore? In that case, this PR is not very interesting, I will do one again when your modifications will be merged.

[akhenakh]

We want to keep the bleve indexer for zim files not containing xapian indexes, and for non cgo env.

So we will keep both solutions.