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.

docs/api/props.md

@@ -189,21 +189,6 @@ getOptionLabel: {
 },
 ```
 
-## onChange
-
-An optional callback function that is called each time the selected
-value(s) change. When integrating with Vuex, use this callback to trigger
-an action, rather than using `v-model` to retrieve the selected value.
-
-```js
-onChange: {
-	type: Function,
-	default: function(val) {
-		this.$emit("input", val);
-	}
-},
-```
-
 ## onTab
 
 Select the current value if `selectOnTab` is enabled
@@ -311,7 +296,7 @@ User defined function for adding Options
 createOption: {
 	type: Function,
 	default(newOption) {
-		if (typeof this.mutableOptions[0] === "object") {
+		if (typeof this.optionList[0] === "object") {
 			newOption = { [this.label]: newOption };
 		}
 		this.$emit("option:created", newOption);