RELEASE-2.0.0a4

Features:

 - Add support for installing from a remote package.xml [saltybeagle]
 - Display version and stability in list-packages [saltybeagle]
 - Improve error when phar includes are disabled by suhosin [mfonda]
 - Replace config-show with allowing people to call the get command without any arguments to achieve the same result.
   "php pyrus.phar get" and php "pyrus.phar config-show" are the same
 - Dropped the channel-add command in favor of channel-discover as they were doing the same thing.

Bug Fixes/Refactoring:

 - Improve error message for plugin installation failures [saltybeagle]
 - Correct exit codes when pyrus fails from CLI [saltybeagle]
 - Packaged license files should use 'filesource' not 'path' [saltybeagle]
 - Removed the PEAR2 namespace and made Pyrus the top level namespace.
   This means all includes and classes need to drop the PEAR2 portion [helgi]
 - Use the channel name instead of package name when giving the security error of when a package claims
   to be from channel X but really is Y (pyrus/Pyrus#50) [xc]
 - DOMDocument::schemaValidate doesn't support phar:// stream [tyrael]