code: public static ConfigurationLoader fromEnvironmentVariables() throws IOException {
          TreeMap<String, String> m = new TreeMap<String, String>(new Comparator<String>() {
              public int compare(String o1, String o2) {
                  return o1.compareToIgnoreCase(o2);
              }
          });
          m.putAll(System.getenv());
          return from(m);
      }
docs: Creates {@link ConfigurationLoader} that uses environment variables as the source.
  
  Since environment variables are often by convention all caps, while system properties
  and other properties tend to be camel cased, this method creates a case-insensitive configuration
  (that allows retrievals by both "path" and "PATH" to fill this gap.