Add example for custom weight and couplings

[rocreguant]

[sacdallago]

FYI: You can get tons of examples for alignments from evcouplings.org :

1. Go to evcouplings.org
2. Top-left menu
3. Precomputed jobs
4. All precomputed jobs
5. Select any job ("View job results")
6. Select any "View alignment in alignmentviewer.org" (right click and open in new page as needed).

Here you can also find coupling score files (open "Raw evolutionary couplings (ECs) table" > bottom left "download file").

:)

[rocreguant]

Thanks! I'll look into it :D