all: Bump protobuf to 3.0.2, to fix protoc in CI

protoc no longer builds in 3.0.0 because auto-download of the gmock zip
now fails. 3.0.2 has a fix to autogen:
https://github.com/google/protobuf/commit/bba446bbf2ac7b0b9923d4eb07d5acd0665a8cf0

All that was strictly necessary was to update .travis.yml and
buildscripts/, but it helps our sanity to keep the rest of the protobuf
versions in sync. Lite is left on its existing version, because it did
not see a bump of neither the java library nor the protoc plugin.
diff --git a/build.gradle b/build.gradle
index badb1c8..ce1b55d 100644
--- a/build.gradle
+++ b/build.gradle
@@ -62,7 +62,7 @@
         javaPluginPath = "$rootDir/compiler/build/exe/java_plugin/$protocPluginBaseName$exeSuffix"
 
         guavaVersion = '19.0'
-        protobufVersion = '3.0.0'
+        protobufVersion = '3.0.2'
         protobufNanoVersion = '3.0.0-alpha-5'
 
         configureProtoCompilation = {
@@ -154,6 +154,8 @@
                 protobuf: "com.google.protobuf:protobuf-java:${protobufVersion}",
                 // swap to ${protobufVersion} after versions align again
                 protobuf_lite: "com.google.protobuf:protobuf-lite:3.0.1",
+                // swap to ${protobufVersion} after versions align again
+                protoc_lite: "com.google.protobuf:protoc-gen-javalite:3.0.0",
                 protobuf_nano: "com.google.protobuf.nano:protobuf-javanano:${protobufNanoVersion}",
                 protobuf_plugin: 'com.google.protobuf:protobuf-gradle-plugin:0.8.0',
                 protobuf_util: "com.google.protobuf:protobuf-java-util:${protobufVersion}",