Fix running the module directly
Fix running the module directly

After rearranging the package structure, running the rivescript module
directly stopped working due to relative import errors. Fix it so that
it can be run directly while still working when imported as normal.

Dinh-Hung-Tu/rivescript-python,Dinh-Hung-Tu/rivescript-python,plasmashadow/rivescript-python,FujiMakoto/makoto-rivescript,Dinh-Hung-Tu/rivescript-python,FujiMakoto/makoto-rivescript,aichaos/rivescript-python,plasmashadow/rivescript-python,FujiMakoto/makoto-rivescript,plasmashadow/rivescript-python,aichaos/rivescript-python,aichaos/rivescript-python