ndn-cxx: Add conflict with ndn.cxx-security-tools package

Fixes: #3
diff --git a/ndn-cxx/debian/control.precise b/ndn-cxx/debian/control.precise
index f04a090..fbcdfb8 100644
--- a/ndn-cxx/debian/control.precise
+++ b/ndn-cxx/debian/control.precise
@@ -32,3 +32,4 @@
 Architecture: i386 amd64
 Depends: ${shlibs:Depends}, ${misc:Depends}
 Description: NDN C++ library with eXperimental eXtensions and security tools
+Conflicts: ndn.cxx-security-tools