fix Config error, add get()/set()

Config.py

@@ -7,10 +7,16 @@ class Config:
         self.vars = {}
         if os.path.isfile(filename):
             f = open(filename, 'r')
-            eval(f, self.vars)
+            exec(f.read(), self.vars)
 
     def write(self):
         f = open(self.filename, 'w')
         for var in self.vars:
             f.write("%s = %s\n" % (var, repr(self.vars[var])))
         f.close()
+
+    def get(self, var):
+        return self.vars[var] if var in self.vars else None
+
+    def set(self, var, val):
+        self.vars[var] = val