Consistently use single quotes if no variable interpolation is required

Change-Id: I8319629778d0e99eab80ff99894623ab8ebfa9c1
diff --git a/app/build.gradle b/app/build.gradle
index e6db14f..dbc1140 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -2,14 +2,14 @@
 
 android {
     compileSdkVersion 23
-    buildToolsVersion "23.0.2"
+    buildToolsVersion '23.0.2'
 
     defaultConfig {
-        applicationId "com.google.reviewit"
+        applicationId 'com.google.reviewit'
         minSdkVersion 14
         targetSdkVersion 23
         versionCode 1
-        versionName "1.0"
+        versionName '1.0'
     }
     buildTypes {
         release {