[protobuf] categorize as tool and highlight

protocol-buffer-3.html.markdown

@@ -1,19 +1,17 @@
 ---
-language: Protocol Buffers
+category: tool
+tool: Protocol Buffers
 filename: protocol-buffers.proto
 contributors:
     - ["Shankar Shastri", "https://github.com/shankarshastri"]
 ---
-# Protocol Buffers
-
-## Why Protocol Buffers
 
 Protocol buffers are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data – think XML, but smaller, faster, and simpler.
 You define how you want your data to be structured once, then you can use special generated source code to easily write and read your structured data to and from a variety of data streams and using a variety of languages.
 Protocol Buffers are Schema Of Messages. They are language agnostic.
 They can be converted to binary and converted back to message formats using the code generated by the protoc compiler for various languages.
 
-```
+```protobuf
 /*
 * Language Syntax
 */