Add configuration option on init

[Stasi V]

Something like this would be very useful:

Vue.use(vBlur, {
  isBlurred: true,
  opacity: 1,
  filter: "blur(5px)",
  transition: "all .3s linear"
});

[Nicolas del Valle]

@Cmacu Indeed, that would be great, do you mind creating a PR implementing it? I can give you hand if you need it :)