Release 0.2.0

Added
- Following sum with Hasher & Digest implementations:
    * Unix (UNIX `cksum`)
    * FNV 32 in several variants: `FNV1-32`, `FNV1a-32` and `FNV0-32`
    * FNV 64 in several variants: `FNV1-64`, `FNV1a-64` and `FNV0-64`
- Paper & reference about CRC32, CRC32c, Adler32 and UNIX checksum.

Fixed
- **CRC32/CRC32C**: Useless NOT operations before/after each block write, replaced by
  a single NOT operation in the `finish` method (and initialisation to `0xFFFFFFFF`).

Changed
- Implementation of unit tests to use private macros module
- Names of checksum structs to follow Rust naming conventions (acronyms as single
  CamelCased word): `BSD` -> `Bsd`, `CRC32(C)` -> `Crc32(c)`, `UNIX` -> `Unix`
- Code using bitwise operations to use Rust primitive methods where applicable.
- Structure of the library to nest the `crc32` module inside a `crc` module.

Removed
- [`byte-tools`](https://crates.io/crates/byte-tools) and [`block-buffer`](https://crates.io/$
  dependencies, *crate is now free of any requirement !*

0.1.0

Added:
- Following sums with Hasher & Digest implementations:
    * Adler32
    * BSD checksum (UNIX `sum`)
    * CRC32 (Ethernet variant)
    * CRC32C (Castagnoli polynomial variant)
    * Fletcher16
    * SysV checksum
- Tests and benchmarks generated with the
  [`crypto-tests`](https://crates.io/crates/crypto-tests) crate
- A basic README inspired by the README of the
  [hashes](https://github.com/RustCrypto/hashes) project
- This CHANGELOG file