v1.0.0

• Removed iter u8
• More test vectors for ChaCha12, etc.
• Updated readme
• Fixed a bug in generation of f32 in a range that caused very small values to be 0 (if the 41 most significant bits of the raw u64 value were all 0).
• Fixed the construction of the hasher in nonce_u64 to properly mix in RandomState entropy in the nonce (inspecting the source for DefaultHasher::new revealed that it seemed to use constant keys that are 0).