Initial work towards YAML make file format.
Tests for YAML parsing.
Restores support for stdin make files for both formats.
Fixing case sensitivity issue.
Support .yml files in recursion.
Additional yaml test.
Updating docs.
Look for drupal-org.make.yml as well.
Switch most docs to yml syntax.
Use the YAML example file in the docs topic.
Merge pull request #970 from drush-ops/yaml-format

YAML make file format.