Pull onTab up to prop, add test

src/components/Select.vue

@@ -549,6 +549,18 @@
         }
       },
 
+      /**
+       * Select the current value if selectOnTab is enabled
+       */
+      onTab: {
+        type: Function,
+        default: function () {
+          if (this.selectOnTab) {
+            this.typeAheadSelect();
+          }
+        },
+      },
+
       /**
        * Enable/disable creating options from searchInput.
        * @type {Boolean}
@@ -927,16 +939,6 @@
         }
       },
 
-      /**
-       * Select the current value if selectOnTab is enabled
-       * @return {void}
-       */
-      onTab() {
-        if (this.selectOnTab) {
-          this.typeAheadSelect();
-        }
-      },
-
       /**
        * Determine if an option exists
        * within this.mutableOptions array.