Merge pull request #268 from clearr/fix-index-leaks

Fix memory leaks in NewIndex() and OpenIndex()
diff --git a/index.go b/index.go
index 0174dc1..1eb5e9d 100644
--- a/index.go
+++ b/index.go
@@ -97,7 +97,7 @@
 		return nil, MakeGitError(err)
 	}
 
-	return &Index{ptr: ptr}, nil
+	return newIndexFromC(ptr), nil
 }
 
 // OpenIndex creates a new index at the given path. If the file does
@@ -115,7 +115,7 @@
 		return nil, MakeGitError(err)
 	}
 
-	return &Index{ptr: ptr}, nil
+	return newIndexFromC(ptr), nil
 }
 
 // Path returns the index' path on disk or an empty string if it