fix: constructor name support for IE11

Author: Samuell1

src/components/MdAutocomplete/MdAutocomplete.vue

@@ -192,7 +192,7 @@
           this.showOptions()
         }
 
-        if (this.searchTerm.constructor.name.toLowerCase() !== 'inputevent') {
+        if (this.searchTerm.constructor.toString().match(/function (\w*)/)[1].toLowerCase() !== 'inputevent') {
           this.$emit('md-changed', this.searchTerm)
         }
       },

src/components/MdField/MdFieldMixin.js

@@ -21,7 +21,7 @@ export default {
         return this.localValue
       },
       set (value) {
-        if (value.constructor.name.toLowerCase() !== 'inputevent') {
+        if (value.constructor.toString().match(/function (\w*)/)[1].toLowerCase() !== 'inputevent') {
           this.$nextTick(() => {
             this.localValue = value
           })

src/components/MdRipple/MdRipple.vue

@@ -52,7 +52,7 @@
     watch: {
       mdActive (active) {
         const isBoolean = typeof active === 'boolean'
-        const isEvent = active.constructor.name.toLowerCase() === 'mouseevent'
+        const isEvent = active.constructor.toString().match(/function (\w*)/)[1].toLowerCase() === 'mouseevent'
 
         if (isBoolean && this.mdCentered && active) {
           this.startRipple({