Request: please accommodate asyncio

[davidmcnabnz]

This is not reporting an error.

This is a request for explicit accommodation for using py-lmbd in asyncio programming environment, including:

• Mention of asyncio usage
• Indication of impacts of lmdb read and write calls on asyncio event loops
• If py-lmdb reads and /or writes are unsafe with asyncio event loops, then provide asyncio-safe wrappers with examples

[jnwatson]

That's fair. I'll keep this open to track adding to the documentation. In the meantime, consider my response here: #316