Release v0.2

* Completely overhauled the cache.
  The cache itself is now fully concurrent,
  which allows it to handle concurrent I/O requests
  as well as make use of parallelism to improve throughput.
  * The FUSE driver does not make explicit use of this feature yet
    though.
* Added encryption.
  Originally, encryption was not going to be implemented and instead
  left over to block drivers.
  However, after some consideration it was decided it would be
  beneficial to support encryption directly to improve performance.
  and for ease of use.
  While a key can either be derived from a password or supplied
  directly, the tools currently only support passwords.
* Add support for mirroring and error correction.
  The tools do not expose any options for multi-disk setups however.
  This will be implemented in v0.2.1