Threadsafe

[mr-tron]

I think, that this library not threadsafe and it affects only encrypted database. I use it something like that - https://play.golang.org/p/u15ttN2661 And then I encrypt database, parallels write records broke my database.

I see, that similar library https://github.com/mutecomm/go-sqlcipher/commit/e4f3941ae62436b717b97b806f7669a9df1089c8 use special patch for crypt library.