Merge pull request #3 from cftp/develop

Adds two filters and composer.json
This will be easier with a class. Refactor to singleton pattern.
Start to abstract functionality so we can reuse in the WP CLI command. Store warnings and info messages in an array and output as HTML for the web triggered operation.
“X posts and Y images” seems clearer to me than “X posts with Y images”.
Get the error message if sideloading fails.
Implements the WP CLI command class
We don’t seem to be using `$uploads` or `$baseurl`?
Everything public!
Remove args, as they aren’t needed.
Convert command seems to work.
Implement progress bar.