Minor changes to README instructions for ex 2. Minor changes to cypher.cpp so it compiles without completition of the code

README.md

 
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-2. Al terminar tu código, ve a la función `main` y descomenta la invocación a la función de prueba unitaria `test_cypher2` para que verifiques tu programa.
+2. Al terminar tu código, ve a la función `main`, comenta la invocación a la función de prueba unitaria `test_cypher1` y descomenta la invocación a la función de prueba unitaria `test_cypher2` para que verifiques tu programa.
 
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-2. After you implement the `cypher` function, modify the `main` function so that line that invokes `test_cypher2` is uncommented. Once again, you will not see the app’s graphical user interface until the `test_cypher2` verifications.
+2. After you implement the `cypher` function, modify the `main` function so that the line that invokes `test_cypher2` is uncommented, and the line that invokes `test_cyper1` is commented. Once again, you will not see the app’s graphical user interface until the `test_cypher2` verifications.
  
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cypher.cpp

 
 string cypher(string message, string key){
    
-    
+    string cypheredMsg = "";
+
     // YOUR CODE HERE
-    
+
     return cypheredMsg ;
 
 }