V3 - Remove mutable class properties plus other misc changes (#781)

* Remove the mutableValue prop in the Select component.

* Add back mutable value when Vue Select has to manage its own value.

* Remove mutableOptions, valueAsAarray. Update webpack minifer to use Terser.

* Fix tabbing

* Fix bug with showClearButton

* Fix tests.

* Call clearSelection when possible

* Update dev sandbox to have all three options for setting value.

* Update dev sandbox to display current value

* Remove unused karma test setup.

* Revert onInput name change.

* Use coveralls

* Change this.internalValue to this.$data._value.

* Remove onInput prop and replace with internal method, updateValue.

* Update tests.

* Rename optionObjectComparator to optionComparator.

tests/unit/Dropdown.spec.js

@@ -59,11 +59,6 @@ describe("Toggling Dropdown", () => {
       multiple: true,
       closeOnSelect: false
     });
-    // const vm = new Vue({
-    //   template:
-    //     '<div><v-select ref="select" :options="options" multiple :closeOnSelect="false" :value="value"></v-select></div>',
-    //   components: { vSelect },
-    // }).$mount();
 
     Select.vm.open = true;
     Select.vm.select("one");
@@ -120,7 +115,7 @@ describe("Toggling Dropdown", () => {
     });
 
     Select.vm.search = "foo";
-    Select.vm.onEscape();
+    Select.find('.vs__search').trigger('keyup.esc')
     expect(Select.vm.search).toEqual("");
   });