title: Gradle and proguard: could not find method runProguard() for arguments [true]
body: <p>I've configured the build.gradle as suggested by <a href="http://proguard.sourceforge.net/index.html#manual/gradle.html">Proguard Gradle manual</a></p>
  
  <p>This is root build.gradle</p>
  
  <pre><code>buildscript {
      repositories {
          flatDir dirs: '/home/username/android-sdks/tools/proguard/lib'
          mavenCentral()
      }
      dependencies {                     
          classpath 'com.android.tools.build:gradle:0.5.+'
          classpath ':proguard'
      }
  }
  </code></pre>
  
  <p>Now this is the build.gradle for my project</p>
  
  <pre><code>apply plugin: 'android'
  
  dependencies {
      compile fileTree(dir: 'libs', include: '*.jar')
      compile project(':SomeLibraryProject')
  }
  
  android {
      compileSdkVersion 19
      buildToolsVersion "19.0.0"
  
      sourceSets {
          ...
      }
  
      task runProguardTask(type: proguard.gradle.ProGuardTask) {
      }
  
      signingConfigs {
          debug {
              storeFile file("./keystore/keystore")
              storePassword "******"
              keyAlias "******"
              keyPassword "*******"
          }
  
          release {
              runProguard true
              proguardFile 'proguard-android.txt'
              storeFile file("./releasekey/keystore")
              storePassword "******"
              keyAlias "********"
              keyPassword "*******"
          }
      }
  
      buildTypes {
          release {
              signingConfig signingConfigs.release
          }
      }  
  }
  </code></pre>
  
  <p>And this is the output</p>
  
  <pre><code>$ ./gradlew build
  
  FAILURE: Build failed with an exception.
  
  * Where:
  Build file '/home/username/Documents/eclipse/workspace/repo/ProjectName/build.gradle' line: 49
  
  * What went wrong:
  A problem occurred evaluating project ':ProjectName'.
  &gt; Could not find method runProguard() for arguments [true] on SigningConfigDsl_Decorated{name=release, storeFile=null, storePassword=null, keyAlias=null, keyPassword=null, storeType=null}.
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  
  BUILD FAILED
  
  Total time: 9.14 secs
  </code></pre>
  
  <p>I also wonder why the storeFile, storePassword, keyAlias and keyPassword are null?</p>