Add silicon to travis.yml.

.travis.yml

@@ -26,6 +26,7 @@ env:
     - "TESTDIR=CSharp/nancy"
     - "TESTDIR=CSharp/servicestack"
     - "TESTDIR=C++/cpoll_cppsp"
+    - "TESTDIR=C++/silicon"
     - "TESTDIR=C++/treefrog"
     - "TESTDIR=C++/ULib"
     - "TESTDIR=C++/wt"