Follow the latest changes up to 2014-03-23

related issues of mozilla/rust:
- mozilla/rust#12772  rename std::vec -> std::slice
- mozilla/rust#13028  rename std::vec_ng -> std::vec
- mozilla/rust@0305ed5d22e4  std: Add Vec to the prelude
- mozilla/rust#12907  std: Rename {push,read}_bytes to {push,read}_exact