error complied app

[hassen66]

when i run my app i get an error
Error:(19, 13) Failed to resolve: com.afollestad:material-dialogs:0.4.4

this my build code
buildscript {
repositories {
mavenCentral()
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:1.0.0'
}
}
apply plugin: 'com.android.application'

repositories {
mavenCentral()
jcenter()
}

dependencies {
compile 'com.readystatesoftware.systembartint:systembartint:1.0.3'
compile 'com.android.support:appcompat-v7:21.0.+'
compile 'com.afollestad:material-dialogs:0.6.1.5'
compile 'com.melnykov:floatingactionbutton:1.0.7'
compile 'com.nineoldandroids:library:2.4.0'
compile 'com.github.junrar:junrar:0.7'
compile 'org.apache.commons:commons-compress:1.8.1'
// Google Play Services
compile 'com.google.android.gms:play-services-plus:6.5.87'
compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.3'
compile project(":library1")
compile fileTree(include: '*.jar', dir: 'libs')
}

android {
compileSdkVersion 21
buildToolsVersion "21.1.2"

packagingOptions {
exclude 'proguard-project.txt'
exclude 'project.properties'
exclude 'META-INF/LICENSE.txt'
exclude 'META-INF/LICENSE'
exclude 'META-INF/NOTICE.txt'
exclude 'META-INF/NOTICE'
exclude 'META-INF/DEPENDENCIES.txt'
exclude 'META-INF/DEPENDENCIES'
}

signingConfigs {
release
}
buildTypes {
release {
signingConfig signingConfigs.release
}
}
lintOptions {
abortOnError false
}

sourceSets {
main {
manifest.srcFile 'AndroidManifest.xml'
java.srcDirs = ['src']
resources.srcDirs = ['src']
aidl.srcDirs = ['src']
renderscript.srcDirs = ['src']
res.srcDirs = ['res']
assets.srcDirs = ['assets']
}

// Move the tests to tests/java, tests/res, etc...
instrumentTest.setRoot('tests')

// Move the build types to build-types/<type>
// For instance, build-types/debug/java, build-types/debug/AndroidManifest.xml, ...
// This moves them out of them default location under src/<type>/... which would
// conflict with src/ being used by the main source set.
// Adding new build types or product flavors should be accompanied
// by a similar customization.
debug.setRoot('build-types/debug')
release.setRoot('build-types/release')

}

}

def Properties props = new Properties()
def propFile = new File('signing.properties')

if (propFile.canRead()){
props.load(new FileInputStream(propFile))

if (props !=null &&
props.containsKey('STORE_FILE') &&
props.containsKey('STORE_PASSWORD') &&
props.containsKey('KEY_ALIAS') &&
props.containsKey('KEY_PASSWORD'))
{
android.signingConfigs.release.storeFile = file(props['STORE_FILE'])
android.signingConfigs.release.storePassword = props['STORE_PASSWORD']
android.signingConfigs.release.keyAlias = props['KEY_ALIAS']
android.signingConfigs.release.keyPassword = props['KEY_PASSWORD']
} else {
println 'signing.properties found but some entries are missing'
android.buildTypes.release.signingConfig = null
}

}else {
println 'signing.properties not found'
android.buildTypes.release.signingConfig = null
}

[VishalNehra]

The lib was removed from jCenter as per it's developer. It's back again, and I've configured project with it's latest version. It should be working now.
Don't forget to update your support repo from sdk manager.