Releases versions that are upgraded to use `block-cipher` v0.8 and
`stream-cipher` v0.7.

- `aes-gcm` v0.7.0
- `aes-gcm-siv` v0.8.0
- `aes-siv` v0.4.0
- `ccm` v0.2.0
- `chacha20poly1305` v0.6.0
- `crypto_box` v0.4.0
- `eax` v0.2.0-pre (final release pending resolution of #214)
- `xsalsa20poly1305` v0.5.0