THRIFT-299. doc: binary type isn't documented nor demonstrated in the tutorial

The existence of the "binary" type is now documented in the relevant places. 

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@739702 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/tutorial/tutorial.thrift b/tutorial/tutorial.thrift
index bc199e4..2655bcb 100755
--- a/tutorial/tutorial.thrift
+++ b/tutorial/tutorial.thrift
@@ -21,6 +21,7 @@
  *  i64         Signed 64-bit integer
  *  double      64-bit floating point value
  *  string      String
+ *  binary      Blob (byte array)
  *  map<t1,t2>  Map from one type to another
  *  list<t1>    Ordered list of one type
  *  set<t1>     Set of unique elements of one type