Improve Italian translation.

Inserted a missing "e"

An improved version of the "hack" section.

@mtt87 translated the idiomatic git verbs "merge" and "revert" to
italian. His translation is correct, but as far as I know Italian just
say "fare un merge" o "fare revert" ("fare" meaning "to do").

Also, the expression "e/o" (literally: and/or) is correct, but very
formal. It can be found in official legal documentation, but it's a bit
weird in a web page.

I changed the original @mtt87's translation "hack" => "apportare
modifiche" (literally: "to produce modifications") with "sperimentare
col codice" (literally: "to experiment/play with code") which I find
much more informal and colloquial.

Removed an unecessary comma

In Italian, differently than English, commas are not needed before conjunctions.
So, before an "and" there's no need for a ","

Typo: "ulteriori" rather than "ulterori"

Sentence "Needed on" translated

"Original code" translated as "Versione originale"

Actually, the previous translation "originalmente" is quite correct,
but it sounds a bit weird and it's not that idiomatic.
Most books, for example, when reporting the original title use the
expression

"Titolo originale"

My "Versione original" could be literally translated as
"Original version".

Closes #36.