Update to the last rust-nigthly.

Version of rustc: 0.11.0-pre-nightly (9f8149e185fe55751b8d8675021d2066249abe54 2014-06-25 18:51:21 +0000).

Also rename the `lib*.rs` files to `ncollide*.rs`.
This will prove useful when cargo will be usable with ncollide.