Upgrade to protobuf-3.0.0-beta-2 and protobuf-nano-3.0.0-alpha-5

Update option name that disables protobuf tests.
diff --git a/compiler/README.md b/compiler/README.md
index ce89ca5..e78c08d 100644
--- a/compiler/README.md
+++ b/compiler/README.md
@@ -13,7 +13,7 @@
 
 * Linux, Mac OS X with Clang, or Windows with MSYS2
 * Java 7 or up
-* [Protobuf](https://github.com/google/protobuf) 3.0.0-beta-1 or up
+* [Protobuf](https://github.com/google/protobuf) 3.0.0-beta-2 or up
 
 ## Compiling and testing the codegen
 Change to the `compiler` directory: