add terminal_color module

This module provides generic tools for printing in color on Linux, Mac, and Windows. Most of this implementation was taken from https://github.com/catkin/catkin_tools, but I went over it and improved the documentation and tests. This will be used by catkin_tools and the ROS 2.0 prototype build tools initially, and later with other command line tools in ROS 2.0.

Automated tests were run on Linux and OS X, manually tested ("acceptance testing" done on Windows).

Rendered documentation for this pull request:

http://osrf-pycommon.readthedocs.org/en/terminal_color/