Updating dependencies
Aparently es5 is now default in jshint and is no longer necesary to explicitly define
Option to have retina images scaled down. Closes #1

 - Supports percentages as a destSize.
 - Detects if an image name ends with @2x and sets its destSize by
   default to 50%
 - Bumps version to 0.3.0
Merge branch 'retina'