Adding  load-file to hy-mode

These commits *experimentally* adds load-file into REPL for hy-mode, using what `cmdline.py` uses for `run-file`. At the moment, another possibility would be to call `run-file` from hy.cmdline directly...this however  will append a 0 at the end  (return value of `run-file`) which maybe a bit more confusing I guess.