Only add app:contentInsetStart="0dp"
to the toolbar remove that left space.
So your Toolbar definition look like this
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
app:contentInsetStart="0dp"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
and it look like this