將butterknife外掛版本降為8.4.0

如下：

build.gradle如下：

   buildscript {
    repositories {
        jcenter()
        google()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0'
        classpath 'com.jakewharton:butterknife-gradle-plugin:8.4.0'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}