Basic config support:

 - green                        # load config from $HOME/.green if it exists
 - export GREEN_CONF=zzz; green # load config from file zzz (override $HOME/.green)
 - green -c xxx                 # load config from file xxx (override $GREEN_CONF)

Config file syntax is defined by python's ConfigParser.
Import config from green
Remove singleton attribute from config.get_config() in setUp rather than tearDown
Import configparser/ConfigParser portably across python versions
Must import configparser/ConfigParser portably in config module also
Merge pull request #24 from tbarron/config

Basic config support (branch config) - contributed by tbarron
Adapted Tom Barron's config file contribution.
It still needs to be tied into actual cmdline processing.
- Updated CHANGELOG
- Refactored the (excellent!) test cases to account for the changes I
  made.  Removed the duplicate documentation and unused code.
- Refactored the config loading: 1) Removed the caching 2) Took
  advantage of ConfigParser's native ability to merge multiple config
files.
- Removed trailing whitespace, renamed a few things to be more readable,
  re-spaced between functions and classes (because I like lots of
vertical whitespace)
- Added module documentation to the config module
- Improved the "--config" option description and metavar.
- Moved the config module loading in cmdline until after coverage is
  initialized
- Removed the cmdline module debugging, including the "--cmdcheck"
  debugging option.
- Added debug output to the config loading.
Basic config integration that _ought_ to work.  Time to get those tests written and try it out.
Lined-up assignments looks nice.
Refactored all the config tests so I can re-use a lot of it to test merging configs and cmdline args
Improved readability
Fully tested.
We can't do debug logging in the config module, because whether logging has been enabled or not has not yet been determined, and it causes later logging setup to get messed up.
Fixed the false non-coverage reports
Added debugging output to see which config files were loaded.
Wrapped the config files so that they automatically have a '[green]' section so users don't actually have to add a section header.
Added config file explanation to --help
Updated the readme to point people to 'green --help' for config-file options.
Prepped 1.1.0 release.
Merge branch 'master' into discover