More modifications for SDK 21 build

.travis.yml

@@ -3,7 +3,8 @@ language: android
 android:
   components:
     - build-tools-21.1.1
-    # Don't have any other tools so far, robolectric covers pretty much everything...
+    - android-21
+    - extra-android-support
 
 script:
   - ./gradlew test

build.gradle

@@ -7,6 +7,8 @@ buildscript {
         mavenCentral()
     }
     dependencies {
+        // Version lock the gradle plugin because Kotlin only works with up to 14.2
+        // KT-6181 is open to track this issue
         classpath 'com.android.tools.build:gradle:0.14.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         // NOTE: Do not place your application dependencies here; they belong