[Breakpoints] flexible configuration for responsive

[v-vovk]

Is it possible to add breakpoints to the constructor? It would be great if we can make smth like this:

new Litepicker({
    ...
    numberOfMonths: 2,
    numberOfColumns: 2,
    breakpoints: {
       767: {
           numberOfMonths: 1,
           numberOfColumns: 1
       },
       ....
   }
})

[wakirin]

Nice idea, perhaps it will be included to mobilefriendly plugin.