Use python's logging module

[dafyddstephenson]

This issue is to track the implementation of python's logging. I was hoping to do this with PR #89 but the more I read about logging's capabilities, the more I'd rather implement it carefully.

Key things we'd like to achieve:

• write subprocess output to log files and then hint to the user where they can find these files
• Convert current print statements to logs at the info level
• add debug information throughout the code using logging's debug level

Things to consider:

• Logging has a global configuration that should be set once at the entry point (the best candidate currently would be environment.py)
• "Loggers" can then be set up and re-used to track different things (we could imagine for example a roms_compile_logger
• "Handlers" decide what to do with the logs (to file, to screen, etc.)

So where we set the global configuration, how many loggers we have and what their responsibilities are, and how to handle their output (new file each time with a date string in the filename is what I imagined) is to be decided before implementation.