在Android Studio中错误：任务执行失败':app:dexDebug'

在这里，我在android studio 1.1.0中使用“ Fabric Plugin ”进行Twitter集成（使用twitter登录）

Error:Execution failed for task ':app:dexDebug'.

com.android.ide.common.internal.LoggedErrorException：无法运行命令：/home/dhruv/Dhruv/sdk/build-tools/21.0.2/dx --dex --no-优化--output /家/ Dhruv直升机/ FestEvo /应用程序/生成/中间体/地塞米松/调试--input列表= /家庭/ Dhruv直升机/ FestEvo /应用程序/生成/中间体/ TMP /地塞米松/调试/ inputList.txt错误代码：2输出：意外TOP- LEVEL EXCEPTION：com.android.dex.DexException：多个dex文件定义Lcom / google / gson / JsonSerializer;在com.android.dx.merge.DexMerger.readSortableTypes（DexMerger.java:596）在com.android.dx.merge.DexMerger.getSortedTypes（DexMerger.java:554）在com.android.dx.merge.DexMerger.mergeClassDefs （DexMerger.java:535）在com.android.dx.merge.DexMerger.mergeDexes（DexMerger.java:171）在com.android.dx.merge.DexMerger.merge（DexMerger.java:189）在com.android . dx.command.dexer.Main.mergeLibraryDexBuffers在com.android.dx.command.dexer.Main（Main.java:454）在com.android.dx.command.dexer.Main.runMonoDex（Main.java:302） . 运行（Main.java:245）在com.android.dx.command.dexer.Main.main（Main.java:214）在com.android.dx.command.Main.main（Main.java:106）

这是 build.gradle: 文件

buildscript {
    repositories {
       // jcenter()
        maven { url 'https://maven.fabric.io/public' }
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:1.0.+'
        classpath 'io.fabric.tools:gradle:1.+'
    }
}
apply plugin: 'com.android.application'
apply plugin: 'io.fabric'

repositories{
    flatDir{
        dirs 'libs'
    }
    //jcenter()
    maven { url 'https://maven.fabric.io/public' }
}

android {
    compileSdkVersion 21
    buildToolsVersion "21.0.2"

    defaultConfig {
        applicationId "com.festevo.devtesting"
        minSdkVersion 15
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

configurations {
    all*.exclude group: 'com.android.support', module: 'support-v4'
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    //compile 'com.android.support:appcompat-v7:21.0.3'

    //compile 'com.spotify.sdk:spotifysdk:1.0.0-beta6@aar'
    compile 'com.spotify.sdk:spotifysdk:1.0.0-beta8@aar'
    // NOTE: Version must match!
   // compile 'com.android.support:support-v4:+'

    compile project ('libraries:FacebookSDK')
    compile project ('libraries:simple-crop-image-lib')
    compile project ('libraries:SlidingMenu')
    compile project ('libraries:nineoldandroids')
    compile project ('libraries:google-play-services_lib')
    compile('com.twitter.sdk.android:twitter:1.3.2@aar') {
        transitive = true;
    }

}

请建议我如何解决我的问题，谢谢你提前:)