ruby: Use fully-qualified type name when necessary

- Use full_name() instead of name(), otherwise package names
  are omitted.
- Fix a minor bug on RubyTypeOf(), to replace dotted protobuf
  package name by ruby's module names correctly.

src/compiler/ruby_generator.cc

@@ -55,11 +55,11 @@ namespace {
 // Prints out the method using the ruby gRPC DSL.
 void PrintMethod(const MethodDescriptor *method, const grpc::string &package,
                  Printer *out) {
-  grpc::string input_type = RubyTypeOf(method->input_type()->name(), package);
+  grpc::string input_type = RubyTypeOf(method->input_type()->full_name(), package);
   if (method->client_streaming()) {
     input_type = "stream(" + input_type + ")";
   }
-  grpc::string output_type = RubyTypeOf(method->output_type()->name(), package);
+  grpc::string output_type = RubyTypeOf(method->output_type()->full_name(), package);
   if (method->server_streaming()) {
     output_type = "stream(" + output_type + ")";
   }

src/compiler/ruby_generator_string-inl.h

@@ -115,6 +115,7 @@ inline grpc::string RubyTypeOf(const grpc::string &a_type,
     return res;
   } else {
     std::vector<grpc::string> prefixes_and_type = Split(res, '.');
+    res.clear();
     for (unsigned int i = 0; i < prefixes_and_type.size(); ++i) {
       if (i != 0) {
         res += "::";  // switch '.' to the ruby module delim