Create happygrep.rb

As per [comment on #6053 in homebrew-cask](https://github.com/caskroom/homebrew-cask/pull/6043#issuecomment-54752432).
Added Dockdrop 1.5.3

App to upload via ftp/webdav/scp by dropping the file onto the icon
Merge pull request #15 from caskroom/fix-8

Added Dockdrop 1.5.3
Delete happygrep.rb

They seem to [have reached an agreement](https://github.com/happypeter/happygrep/issues/6), and the official version was [submitted to the main repo](https://github.com/caskroom/homebrew-cask/pull/6086).