Add tasks for all the new languages

Task/Symmetric-difference/Lasso/symmetric-difference.lasso

@@ -0,0 +1,24 @@
+[
+var(
+    'a'  = array(
+       'John'
+      ,'Bob'
+      ,'Mary'
+      ,'Serena'
+    )
+
+   ,'b'  = array
+
+);
+
+$b->insert( 'Jim' ); // Alternate method of populating array
+$b->insert( 'Mary' );
+$b->insert( 'John' );
+$b->insert( 'Bob' );
+
+$a->sort( true ); // arrays must be sorted (true = ascending) for difference to work
+$b->sort( true );
+
+$a->difference( $b )->union( $b->difference( $a ) );
+
+]