Teach grok_tweets.py about prefix directory (-d)
subr_misc.py: quick fix to work with absolute paths
grok_tweets.py: remove hardcoded filter
grok_tweets.py: skip links to the homepage
Merge branch 'master' of github.com:bassosimone/rivoluzionedigitale
index.md: update who is doing what
index.md: replay changes by daviderudy93 that I reverted before

I needed, previously, to revert a contribution from @daviderudy93
because it was fucked up during the merge.

Now, I have applied again the diff, having removed all the noise.