Upgrade to Guava 26.0-android and jsr305 3.0.2
diff --git a/core/build.gradle b/core/build.gradle
index 700592f..4a24290 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -3,12 +3,19 @@
 dependencies {
     compile project(':grpc-context'),
             libraries.gson,
-            libraries.guava,
             libraries.errorprone,
             libraries.jsr305,
             libraries.animalsniffer_annotations
+    compile (libraries.guava) {
+        // prefer 2.2.0 from libraries instead of 2.1.3
+        exclude group: 'com.google.errorprone', module: 'error_prone_annotations'
+        // prefer 3.0.2 from libraries instead of 3.0.1
+        exclude group: 'com.google.code.findbugs', module: 'jsr305'
+        // prefer 1.17 from libraries instead of 1.14
+        exclude group: 'org.codehaus.mojo', module: 'animal-sniffer-annotations'
+    }
     compile (libraries.opencensus_api) {
-        // prefer 3.0.0 from libraries instead of 3.0.1
+        // prefer 3.0.2 from libraries instead of 3.0.1
         exclude group: 'com.google.code.findbugs', module: 'jsr305'
         // prefer 20.0 from libraries instead of 19.0
         exclude group: 'com.google.guava', module: 'guava'
@@ -16,7 +23,7 @@
         exclude group: 'io.grpc', module: 'grpc-context'
     }
     compile (libraries.opencensus_contrib_grpc_metrics) {
-        // prefer 3.0.0 from libraries instead of 3.0.1
+        // prefer 3.0.2 from libraries instead of 3.0.1
         exclude group: 'com.google.code.findbugs', module: 'jsr305'
         // we'll always be more up-to-date
         exclude group: 'io.grpc', module: 'grpc-context'