Versions managing of dependencies in Gradle

module-build.gradle

apply plugin: 'com.android.application'
apply plugin: 'android-apt'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"

    defaultConfig {
        applicationId "com.alexzh.temperatureconverter"
        minSdkVersion 14
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        debug {
            testCoverageEnabled true
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile "com.android.support:appcompat-v7:$supportLibVersion"
    compile "com.android.support:design:$supportLibVersion"
    compile "com.android.support:preference-v14:$supportLibVersion"

    //ButterKnife
    compile "com.jakewharton:butterknife:$butterknifeLibVersion"
    apt "com.jakewharton:butterknife-compiler:$butterknifeLibVersion"

    //events
    compile "org.greenrobot:eventbus:$eventbusLibVersion"

    //di
    compile "com.google.dagger:dagger:$daggerLibVersion"
    apt "com.google.dagger:dagger-compiler:$daggerLibVersion"
    provided 'javax.annotation:jsr250-api:1.0'

    //retrofit
    compile "com.squareup.retrofit2:retrofit:$retrofitLibVersion"

    //gson
    compile "com.squareup.retrofit2:converter-gson:$retrofitLibVersion"

    //junit
    testCompile "junit:junit:$junitLibVersion"

    //mockito
    testCompile "org.mockito:mockito-core:$mockitoLibVersion"

    //espresso
    androidTestCompile("com.android.support.test.espresso:espresso-core:$espresspLibVersion") {
        exclude group: 'com.android.support', module: 'support-annotations'
    }
    androidTestCompile("com.android.support.test:runner:$testRunnerLibVirsion") {
        exclude group: 'com.android.support', module: 'support-annotations'
    }
    androidTestCompile("com.android.support.test.espresso:espresso-intents:$espresspLibVersion") {
        exclude group: 'com.android.support', module: 'support-annotations'
    }

    //uiautomator
    androidTestCompile "com.android.support.test.uiautomator:uiautomator-v18:$uiautomatorLibVersion"
}

root-build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.2'

        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

ext {
    supportLibVersion = '25.0.0'
    butterknifeLibVersion = '8.2.1'
    daggerLibVersion = '2.0.2'
    retrofitLibVersion = '2.1.0'
    eventbusLibVersion = '3.0.0'
    junitLibVersion = '4.12'
    mockitoLibVersion = '1.10.19'
    uiautomatorLibVersion = '2.1.2'
    espresspLibVersion = '2.2.2'
    testRunnerLibVirsion = '0.5'
}