How to implement Robobinding in android app

Question

I'm trying to implement the MVVM architecture using Robobinding. Here's the link I'm following for the Environment setup of Robobinding in Android Studio(without AspectJ): http://robobinding.github.io/RoboBinding/getting_started.html#_android_studio

This is what my app level Build.gradle looks like after adding the dependencies:

apply plugin: 'com.android.application'
apply plugin: 'com.neenbedankt.android-apt'
android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"
    defaultConfig {
        applicationId "com.example.simpletimerapp"
        minSdkVersion 14
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}
dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'

    compile "org.robobinding:robobinding:${robobindingVersion}"
}
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.+'
    }
}

The problem is gradle build fails with the following error:

Error:(26, 0) Could not find property 'robobindingVersion' on org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler_Decorated@2ccd2d42. Open File

EDIT 1:

On replacing ${robobindingVersion} in the dependencies block with 0.8.12 (latest version of robobinding), gradle build finishes successfully. But now, I'm unable to use the "bind" attribute in the views in my layout files. This is the error:

Unexpected namespace prefix "bind" found for tag TextView

EDIT 2:

Still can't find the solution. So, I downloaded this minimal android app (from their official github page) which implements robobinding and edited it to create my own app. It's working fine now.