fix 在Android环境下，小米、华为都只能选择图片，没有拍照选项。需在input标签上加capture属性 Tencent#22

Author: bearyan

example/index.html

@@ -165,7 +165,7 @@
                             <div class="weui-uploader__bd">
                                 <ul class="weui-uploader__files" id="uploaderFiles"></ul>
                                 <div class="weui-uploader__input-box">
-                                    <input id="uploaderInput" class="weui-uploader__input" type="file" accept="image/*" multiple="">
+                                    <input id="uploaderInput" class="weui-uploader__input" type="file" accept="image/*" capture="camera" multiple="" />
                                 </div>
                             </div>
                         </div>