Add feature Multi Select Month

[lillo42]

Hi,

I have implement Multi Select Month,

I add 2 new properties.
MultiSelect: boolean
Separetor: string

if Multiselect is active, will accept select multi month and will put on input all month select separete by separetor.

[benjamin-albert]

Thanks for opening a pull request and helping make this plugin better for everyone!

I just fetched your changes and messed with the demo to take a look at the new feature.

Looks really nice!

As you can see from the Travis-CI Build some tests are failing (some things broke).

We need those tests to pass before we can merge.

So we have two options:

1. You run the tests and fix them.

2. We fetch your changes and fix the tests.

I personally learned a lot form writing tests for this project and I think you can learn a lot form this to.

If you you need any help running/updating the tests we wi'll be more than happy to help.

[lillo42]

Thank you :), as soon as I will run the test and fixed. And make some example how use,