Explain more clearly that days of the month are not padded by default
I have improved the README.md file to explain better that hours and days of the month are not padded by default. Since documentation uses 24th and there is a note about padding only for months, some users may think the rest of the components are padded automatically.
In addition, I have added some unit tests to verify that the days of the month are properly padded in index.spec.js. My initial intention was to avoid changes in the rest of the file, but I thought that keeping a single date for all the tests as you were doing was more appropriate, so I have changed the day of the month and updated the unit tests accordingly.
By the way, thank you for this library; it is very useful for the projects I work on.