The code that we have actually implements XTUCK and not TUCK. And it's a bit
broken, so fix it and add some tests. The most interesting one (that required
to touch stack code) is the one when we have 1 element on the stack and are
trying to tell XTUCK to push 2 elements deep.
* support VM to pass method and arguments to a script.
* added support for type assertions in smartcontracts.
* added native vm support for print.
* moved VM API packages to vm -> API
* reverted the native Print opcode in favor of runtime.Log
* added support for registering custom interop hooks in the VM.
* Updated README
* Updated compiler with @OPTIMIZE tags
* Moved more tests to VM package.
* optimized and refactored compiler and vm API
* updated README with new smartcontract apis
* bumped version