Fixed compilation warnings

app/build.gradle

@@ -12,21 +12,25 @@ android {
         versionName "0.1.0"
         vectorDrawables.useSupportLibrary = true
     }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
 }
 
 dependencies {
-    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
-    compile "com.android.support:appcompat-v7:$support_version"
-    compile "com.android.support:design:$support_version"
-    compile "com.android.support:support-vector-drawable:$support_version"
-    compile 'com.android.support.constraint:constraint-layout:1.1.0-beta4'
-    compile 'io.reactivex.rxjava2:rxjava:2.1.8'
-    compile 'io.reactivex.rxjava2:rxkotlin:2.1.0'
-    compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
-    compile 'com.tbruyelle.rxpermissions2:rxpermissions:0.9.4@aar'
-    compile "com.squareup.retrofit2:retrofit:$retrofit_version"
-    compile "com.squareup.retrofit2:adapter-rxjava2:$retrofit_version"
-    compile "com.squareup.retrofit2:converter-gson:$retrofit_version"
-    compile 'com.github.bumptech.glide:glide:4.4.0'
-    compile(name: 'ulogin-sdk-v1.1', ext: 'aar')
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
+    implementation "com.android.support:appcompat-v7:$support_version"
+    implementation "com.android.support:design:$support_version"
+    implementation "com.android.support:support-vector-drawable:$support_version"
+    implementation 'com.android.support.constraint:constraint-layout:1.1.0-beta4'
+    implementation 'io.reactivex.rxjava2:rxjava:2.1.8'
+    implementation 'io.reactivex.rxjava2:rxkotlin:2.1.0'
+    implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
+    implementation 'com.tbruyelle.rxpermissions2:rxpermissions:0.9.4@aar'
+    implementation "com.squareup.retrofit2:retrofit:$retrofit_version"
+    implementation "com.squareup.retrofit2:adapter-rxjava2:$retrofit_version"
+    implementation "com.squareup.retrofit2:converter-gson:$retrofit_version"
+    implementation 'com.github.bumptech.glide:glide:4.4.0'
+    implementation(name: 'ulogin-sdk-v1.1', ext: 'aar')
 }