Build instructions: `cd ../contrib` -> `cd contrib`

The build instructions pointed to a wrong location of the `contrib`
directory

Change-Id: Ib7d00b6423509cb0001eba2beedd9732fb74a8c7
Tuleap: #638

README

@@ -62,7 +62,7 @@ How to compile on Linux
 
 1) Compile the dependencies first
 
-cd ../contrib/
+cd contrib
 mkdir native
 cd native
 ../bootstrap