use custom proguard config for running tests

The new Android Testing Support library stuff causes proguard to freak
out, so make proguard ignore all that stuff when running tests.

app/build.gradle

@@ -132,6 +132,7 @@ android {
             minifyEnabled true
             shrinkResources true
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            testProguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro', 'src/androidTest/proguard-rules.pro'
         }
         debug {
             testCoverageEnabled = true

app/src/androidTest/proguard-rules.pro

@@ -0,0 +1,16 @@
+-dontwarn android.test.**
+-dontwarn android.support.test.**
+-dontnote junit.framework.**
+-dontnote junit.runner.**
+
+# Uncomment this if you use Mockito
+#-dontwarn org.mockito.**
+
+-keep class org.hamcrest.** { *; }
+-dontwarn org.hamcrest.**
+
+-keep class org.junit.** { *; }
+-dontwarn org.junit.**
+
+-keep class junit.** { *; }
+-dontwarn junit.**