Bump mockito to version 2.21.0

Author: mabae

mockito-kotlin/build.gradle

@@ -27,7 +27,7 @@ dependencies {
     compileOnly "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
     compileOnly 'org.jetbrains.kotlinx:kotlinx-coroutines-core:0.23.3'
 
-    compile "org.mockito:mockito-core:2.19.0"
+    compile "org.mockito:mockito-core:2.21.0"
 
     testCompile 'junit:junit:4.12'
     testCompile 'com.nhaarman:expect.kt:1.0.0'
@@ -55,4 +55,4 @@ kotlin {
     experimental {
         coroutines "enable"
     }
-}
+}