通过自定义属性来设置图片的圆形， 圆角， 边框，及边框颜色。
<com.suguiming.android_roundimageview.RoundImageView
xmlns:app="http://schemas.android.com/apk/res-auto"
android:src="proxy.php?url=https%3A%2F%2Fgithub.com%2F%40mipmap%2Fround_test"
android:layout_width="100dp"
android:layout_height="100dp"
app:imageType="corner_image"
app:borderColor="@color/purple"
app:border="10dp"
app:cornerRadius="10dp" />
