Escape quotations in statements (fixes #4)

src/main/java/tfm/graphs/CFGGraph.java

@@ -46,7 +46,7 @@ public class CFGGraph extends Graph {
 
         String nodes = getNodes().stream()
                 .sorted(Comparator.comparingInt(GraphNode::getId))
-                .map(node -> String.format("%s [label=\"%s: %s\"]", node.getId(), node.getId(), node.getData()))
+                .map(GraphNode::toGraphvizRepresentation)
                 .collect(Collectors.joining(lineSep));
 
         String arrows =

src/main/java/tfm/nodes/GraphNode.java

@@ -145,7 +145,9 @@ public class GraphNode<N extends Node> extends Vertex<String, ArcData> {
     }
 
     public String toGraphvizRepresentation() {
-        return String.format("%s[label=\"%s: %s\"];", getId(), getId(), getData());
+        String text = getData().replace("\\", "\\\\")
+                .replace("\"", "\\\"");
+        return String.format("%s[label=\"%s: %s\"];", getId(), getId(), text);
     }
 
     public Set<String> getDeclaredVariables() {