NaCl is basically this, but as a library instead of copy/paste. It's available in most languages if you look around.

https://nacl.cr.yp.to/index.html

https://golang.org/x/crypto/nacl for the Gophers among us (it provides only box/secret_box, though)

You could argue that https://tweetnacl.cr.yp.to/ is well-suited to cut-and-paste crypto.

You can basically `go get` this and use it as it is though. I'm not entirely sure why they spin it as copy-pasta crypto.

.NET is covered: http://securitydriven.net/inferno/