Error:The project is using an unsupported version of the Android Gradle plug-in (0.12.2)

Use this version of gradle plugin

classpath 'com.android.tools.build:gradle:1.0.0-rc4'

For more info related to gradle plugin and android studio compatiblity refer this

Edit

As of now both android studio as well as gradle plugin are both stable hence use this

classpath 'com.android.tools.build:gradle:1.0.0'

In App build.gradle in buildTypes{} i think you using runproguard. runProguard is depreceated so use minifyEnabled instead of runproguard

Edited :

buildTypes {
    release {
        runProguard false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
    }
}

update answer

buildTypes {    
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
    }
}

You have to update your classpath. Currently I've got:

classpath 'com.android.tools.build:gradle:1.0.0-rc4'

Edit:

Replace runProguard with minifyEnabled in your gradle build file