Fixed SASM::RASM::Builder #to_program and added #to_instructions

The Builder can now import from a file using load_file
Implemented import and load commands

import:
Loads a file and executes the instructions immediately using SlateVM#exec

load:
Loads a file and writes it into memory
lsopcode is now an executable file
Updated RASM examples
Callback > Callbacks

Better naming convention, since Callback can actually host multiple
callbacks
Added some missing requires
Added some RASM debug features

Since RASM is ruby and we use instance_eval to load the file contents,
things get messy when it fails, as the backtrace does not exist.
Version bump 1.5.1 + Gemfile