Change Tree to use Vec instead of ~[]. Change read to use Vec instead of ~[] as well, since ~[] no longer implements push().
~string was removed from rust master. rework read and eval to work with this
Fix compilation errors due to latest Rust master
I guess all the cool kids are using String instead of ~str now. This commit changes string stuff until it compiles
Merge because git told me I had to (even though its wrong)