doc: Use fenced code block for syntax highlighting

Credit: @adius
Reviewed-By: @othiym23
PR-URL: #61

README.md

@@ -19,31 +19,33 @@ nice option parser.
 
 ## USAGE
 
-    // my-program.js
-    var nopt = require("nopt")
-      , Stream = require("stream").Stream
-      , path = require("path")
-      , knownOpts = { "foo" : [String, null]
-                    , "bar" : [Stream, Number]
-                    , "baz" : path
-                    , "bloo" : [ "big", "medium", "small" ]
-                    , "flag" : Boolean
-                    , "pick" : Boolean
-                    , "many1" : [String, Array]
-                    , "many2" : [path]
-                    }
-      , shortHands = { "foofoo" : ["--foo", "Mr. Foo"]
-                     , "b7" : ["--bar", "7"]
-                     , "m" : ["--bloo", "medium"]
-                     , "p" : ["--pick"]
-                     , "f" : ["--flag"]
-                     }
-                 // everything is optional.
-                 // knownOpts and shorthands default to {}
-                 // arg list defaults to process.argv
-                 // slice defaults to 2
-      , parsed = nopt(knownOpts, shortHands, process.argv, 2)
-    console.log(parsed)
+```javascript
+// my-program.js
+var nopt = require("nopt")
+  , Stream = require("stream").Stream
+  , path = require("path")
+  , knownOpts = { "foo" : [String, null]
+                , "bar" : [Stream, Number]
+                , "baz" : path
+                , "bloo" : [ "big", "medium", "small" ]
+                , "flag" : Boolean
+                , "pick" : Boolean
+                , "many1" : [String, Array]
+                , "many2" : [path]
+                }
+  , shortHands = { "foofoo" : ["--foo", "Mr. Foo"]
+                 , "b7" : ["--bar", "7"]
+                 , "m" : ["--bloo", "medium"]
+                 , "p" : ["--pick"]
+                 , "f" : ["--flag"]
+                 }
+             // everything is optional.
+             // knownOpts and shorthands default to {}
+             // arg list defaults to process.argv
+             // slice defaults to 2
+  , parsed = nopt(knownOpts, shortHands, process.argv, 2)
+console.log(parsed)
+```
 
 This would give you support for any of the following: