Turns on code coverage for sample app

Author: StylingAndroid

sample/build.gradle

@@ -13,6 +13,9 @@ android {
  testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
+ debug {
+ testCoverageEnabled true
+ }
  release {
  minifyEnabled false
  proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'