Remove the confusing `tree` API. It should be recreated later.

servo · metajack · May 3, 2013 · May 2, 2013 · May 3, 2013 · May 3, 2013
commit 88cd77f4d620e5232ac455f6cf554767903c637b
diff --git a/src/servo/util/mod.rs b/src/servo/util/mod.rs
@@ -5,6 +5,5 @@
 pub use servo_util::cache;
 pub use servo_util::time;
 
-pub mod tree;
 pub mod task;
 
diff --git a/src/servo/util/tree.rs b/src/servo/util/tree.rs