Fix compilation failure on latest rust-nightly

&[1u8, 2, 3, 4] seems to be of type &[u8, ..4] instead of type &[u8],
use [1u8, 2, 3, 4].as_slice() instead
Removed unused attributes

These attributes led to compiler warnings with the latest rust-compiler.
Preparations for uploading to crates.io
Merge remote-tracking branch 'origin/master' into libsodium-sys

Conflicts:
	Cargo.toml