Added Italian Holidays based on Google Calendar of Italian Holidays

[lbrutti]

Added locale/italy.js

Ran npm test with the following output:

$ npm test
> moment-holiday@1.5.1 test V:\repoPvt\moment-holiday
 >jshint *.js locale/*.js && ava

ERROR: Can't open *.js
ERROR: Can't open locale/*.js
40 passed

Ran the same tests on master branch with same results.

[dbaccello]

San Silvestro 12/31 is not holiday in Italy, it should be removed.