changed the way to launch the tale driver from 'python -m tale.driver' to 'python -m tale.main'
added main module that contains the most convenient ways to launch the driver
story scripts now use this new module
introduced StoryConfig class to replace the free format story config dict
fixed python 3.4 warning concerning unescape function deprecation
got rid of unnecessary ReadonlyAttribues class complexity, Context is now a simple class