Adding read-only mode where user cannot pick a date

[JayHuang]

Adding read-only option: read-only="true"

This makes the directive not trigger the popup, preventing the user from selecting a date.

See bottom form, data updates according to the model using $watch, but user cannot manually edit End Date.

[JayHuang]

Calendar still toggles for this version on tab focus, update coming.

Edit: Updated, see commit below.

[novarac23]

@JayHuang Hey mate! This looks like an interesting feature and I think I would like to merge it to master 👍 But I see there are some conflicts, do you mind taking a look at those ? I am willing to do pair programming if needed to fix these :)

[JayHuang]

@novarac23 I don't use ngQuickDate anymore, but I have created a new fork and submitted the same PR at #119 with conflicts resolved (dist files).

Worth noting that ngQuickDate is failing 8 tests, but this occurs regardless of the changes in my PR.

[novarac23]

@JayHuang Ok cool!

Closing this pr and gonna reference #119 for the fix! Thanks a lot for the effort mate! 🙌