modifying headings for tree traversal chapter

Author: leios

chapters/fundamental_algorithms/tree_traversal.md

@@ -158,7 +158,7 @@ Do you think we should be using real code snippets in the main text or stick the
 
 # Example Code
 
-### C++
+### C++:
 
 ```cpp
 /*-------------simple_tree_traversal.cpp--------------------------------------//
@@ -250,7 +250,7 @@ int main(){
 
 ```
 
-### Python
+### Python:
 
 ```Python
 
@@ -330,7 +330,7 @@ main()
 
 ### C
 
-```C
+```C:
 // Submitted by Gathros
 #include <stdio.h>
 #include <stdlib.h>
@@ -490,6 +490,8 @@ int main() {
 }
 ```
 
+#### C#:
+
 ```cs
 // submitted by Julian Schacher‏
 using System;