Cleaned up filepicker.io hack as attachment tool

Revert "Merge pull request #1012 from ZogStriP/extract-imgur-support-to-a-gem"

This reverts commit eb91a0c9dfd9484a91d29b014929f16be6bd3ec5, reversing
changes made to 334194ef82b94fb975adfdfa917fc821bf7c32f9.