fixed some components bug that can not translate when using vue-i18n

src/components/select/select.vue

@@ -8,14 +8,14 @@
                 <span class="ivu-tag-text">{{ item.label }}</span>
                 <Icon type="ios-close-empty" @click.native.stop="removeTag(index)"></Icon>
             </div>
-            <span :class="[prefixCls + '-placeholder']" v-show="showPlaceholder && !filterable">{{ placeholder }}</span>
+            <span :class="[prefixCls + '-placeholder']" v-show="showPlaceholder && !filterable">{{ localePlaceholder }}</span>
             <span :class="[prefixCls + '-selected-value']" v-show="!showPlaceholder && !multiple && !filterable">{{ selectedSingle }}</span>
             <input
                 type="text"
                 v-if="filterable"
                 v-model="query"
                 :class="[prefixCls + '-input']"
-                :placeholder="showPlaceholder ? placeholder : ''"
+                :placeholder="showPlaceholder ? localePlaceholder : ''"
                 :style="inputStyle"
                 @blur="handleBlur"
                 @keydown="resetInputState"
@@ -26,7 +26,7 @@
         </div>
         <transition name="slide-up">
             <Drop v-show="visible" ref="dropdown">
-                <ul v-show="notFound" :class="[prefixCls + '-not-found']"><li>{{ notFoundText }}</li></ul>
+                <ul v-show="notFound" :class="[prefixCls + '-not-found']"><li>{{ localeNotFoundText }}</li></ul>
                 <ul v-show="!notFound" :class="[prefixCls + '-dropdown-list']" ref="options"><slot></slot></ul>
             </Drop>
         </transition>
@@ -37,14 +37,14 @@
     import Drop from './dropdown.vue';
     import clickoutside from '../../directives/clickoutside';
     import { oneOf, findComponentDownward } from '../../utils/assist';
-    import { t } from '../../locale';
     import Emitter from '../../mixins/emitter';
+    import Locale from '../../mixins/locale';
 
     const prefixCls = 'ivu-select';
 
     export default {
         name: 'iSelect',
-        mixins: [ Emitter ],
+        mixins: [ Emitter, Locale ],
         components: { Icon, Drop },
         directives: { clickoutside },
         props: {
@@ -65,10 +65,7 @@
                 default: false
             },
             placeholder: {
-                type: String,
-                default () {
-                    return t('i.select.placeholder');
-                }
+                type: String
             },
             filterable: {
                 type: Boolean,
@@ -87,10 +84,7 @@
                 default: false
             },
             notFoundText: {
-                type: String,
-                default () {
-                    return t('i.select.noMatch');
-                }
+                type: String
             }
         },
         data () {
@@ -153,6 +147,20 @@
                 }
 
                 return style;
+            },
+            localePlaceholder () {
+                if (this.placeholder === undefined) {
+                    return this.t('i.select.placeholder');
+                } else {
+                    return this.placeholder;
+                }
+            },
+            localeNotFoundText () {
+                if (this.notFoundText === undefined) {
+                    return this.t('i.select.noMatch');
+                } else {
+                    return this.notFoundText;
+                }
             }
         },
         methods: {