Removed `u`, `d` and `s` format specifiers

See:
https://github.com/rust-lang/rust/pull/19040
https://github.com/rust-lang/rfcs/blob/master/text/0380-stabilize-std-fmt.md
Imported enum namespace, since they are now explicit

See:
https://github.com/rust-lang/rust/commit/3dcd2157403163789aaf21a9ab3c4d30a7c6494d
Made coercions from [T] to &[T] explicit.

See:
https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md
Added external time crate dependency
More [T] to &[T] conversions, and renamed warning specifiers
Fixed serialization test assertions

See http://stackoverflow.com/questions/27089062/comparing-slices-and-lifetimes
Changed erroneous unnecessary_typecasts to unused_typecasts
Merge pull request #29 from abspoel/update-to-nightly

Update to nightly