Fix bug where Command.globs didn't delete the destination directory.
There was often a mix between absolute and relative paths and in the
previous version, the destination argument was usually an absolute
path where the glob array (from Dir['*']) was a relative path.
Using a test_dir helper method for tests.
Rudimentary tests for Jekyll::Command
Added directory_with_contents() to DRY up test code and ensure folders exist in TestCommand.
Using 1.8.7-compliant File.expand_path instead of >1.9 File.realpath
Load in config from --config switch
Add unit tests for custom configuration.
Add --config switch to build and serve commands.
Add test to ensure plugins are executed in order of priority.
Remove the duplication when creating Converters and Generators

Encapsulate it in a method and give the method the class to walk the
subclass tree for to create new objects.
Sort instantiated subclasses in Site.
Added tests for generators.
Newline.
Merge pull request #863 from mojombo/accept-custom-config

Accept custom configuration
Update history to reflect merge of #863
Merge pull request #864 from mojombo/prioritize_plugins

Prioritize plugins & DRY subclass instantiation
Update history to reflect merge of #864.
replace \s with space
Patch for multibyte URI problem. Closes #723.
Update history to reflect merge of #723.