Revert "Fix https issue: Use wp_upload_dir path plus filename, rather than relying on string matching."

This reverts commit 78acfb5784abe2dc936b654ab2c3827653ab9ffe.

This breaks when the year/month of the image being cropped is different from the current year/month. The current method is more reliable, grungy though it is.
Merge pull request #8 from hbrock25/master

Revert "Fix https issue: Use wp_upload_dir path plus filename, rather th...