Added ghRepo.getBlob(String) method

Signed-off-by: Kanstantsin Shautsou <kanstantsin.sha@gmail.com>

src/main/java/org/kohsuke/github/GHTreeEntry.java

@@ -54,14 +54,14 @@ public class GHTreeEntry {
 
 
     /**
-     * SHA1 of this object.
+     * SHA1 of this blob object.
      */
     public String getSha() {
         return sha;
     }
 
     /**
-     * API URL to this Git data, such as
+     * API URL to this Git blob data, such as
      * https://api.github.com/repos/jenkinsci
      * /jenkins/git/commits/b72322675eb0114363a9a86e9ad5a170d1d07ac0
      */