Signer interface instead of private key

[ice-cronus]

for example crypto.Signer could be used.
Needed to detach signing implementation and building of signed message from an actual private key, to use remote signers for example

[ice-cronus]

Oh, it seems to be implemented by #263 May we have a release with it?

[xssnick]

Hi, will be released later, but for now you can use it from dev branch, importing like go get github.com/xssnick/tonutils-go@a0eeb518ae2c2bedea004616df68e90ae9d42cb5