Refactor swapper code with traits.

Change-Id: Ia27d3a11fea86d2ac430c3455d5247cfc4891e70
diff --git a/src/lib.rs b/src/lib.rs
index 62e269a..84e8fdc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,5 +3,4 @@
 
 mod bindings;
 
-pub mod cswap;
-pub mod swap;
+pub mod swapper;