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/.travis.yml b/.travis.yml
index 13b2d01..108a878 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,7 @@
 
 env:
   global:
-    - PROTOBUF_VERSION=3.0.0-beta-1
+    - PROTOBUF_VERSION=3.0.0-beta-2
     - OPENSSL_VERSION=1.0.2d
     - LDFLAGS=-L/tmp/protobuf-${PROTOBUF_VERSION}/lib
     - CXXFLAGS=-I/tmp/protobuf-${PROTOBUF_VERSION}/include