Emit event when inputString attribute are cleared

[rodrigoords]

Description:
When user inputString of UserSettings interface, component load with the configured string correctly, but no event was emitted when the user clears this string, the event only will be fired when address come from component search engine.

To check the issue you can use example 3 of geoautcomplete example list (https://tanoy009.github.io/ng4-geoautocomplete/)
clear the "Bangalore, karnataka" entries end you can check that no event is fired but with you search a new address and clear this address an output event with no input event was fired.
As you can see in my example of userSetting below I'm using the component without the search button.

Lib version: "ng4-geoautocomplete": "^0.1.0"
related issue: #43

Example:

            this.userSettings = {
                geoCountryRestriction: ['br'],
                geoLocation: [this.myLat, this.myLng],
                showSearchButton: false,
                inputPlaceholderText: 'Buscar Endereço',
                noOfRecentSearchSave: 5,
                inputString: 'Some address'
            };