Riffle v2.0.0-alpha.99

• Upgrade b-tree to 2.0.0-alpha.128.
• Upgrade operation to 6.0.0-alpha.13.
• Upgrade b-tree to 2.0.0-alpha.127.
• Upgrade mvcc to 2.0.0-alpha.5.
• Upgrade reciprocate to 0.0.10.
• Upgrade ascension to 3.0.0-alpha.13.
• Upgrade destructible to 7.0.0-alpha.72.
• Upgrade turnstile to 6.0.0-alpha.83.
• Upgrade magazine to 6.0.0-alpha.10.
• Update LICENSE for current year.

Closes #261.