2.4.0

• Added filter for tevkori_get_sizes, with tests
• Added Composer support
• Improved aspect ratio logic
• Cleanup of code style and comments added
• Added PHP 5.2 to our Travis test matrix
• Fixed unit test loading
• Preventing duplicates in srcset array
• Updated docs for advanced image compression
• Bump plugin 'Tested up to:' value to 4.3
• Added 'sudo: false' to travis.ci to use new TravisCI infrastructure
• Removing the srcset and sizes attributes if there is only one source present for the image
• Use edited image hash to filter out originals from edited images
• Make output of tevkori_get_srcset_array filterable
• Readme cleanup, changelog added.