Extend the logging module to support colours.
Pass *args, **kwargs through in the color loggers

Also add msg as an explicit argument to logger.log.
Merge pull request #249 from OP2/color-logger

Extend the logging module to support colours.

Add functions for printing info messages in color:
* info_green
* info_red
* info_blue

Add a helper routine log(level, message) to log a given message
at a given log level.