Fix when $_APTMGR is full path. Closes ilikenwf#188

Update README.md

 * Linux Mint apt not supported because it's a custom shell script there.

Add missing tag to zsh completion

Fix DLDIR default directory. Closes ilikenwf#162

 * Set /var/cache/apt/apt-fast as default directory over
   /var/cache/apt/archives/apt-fast .

   Prevents apt warning:

    W: Problem unlinking the file apt-fast - pkgAcquire::Clean (21: Is a directory)

 * Update README and fix language in config file.

Add GPL v3 licence. Closes ilikenwf#160

Support metalink redirection as default.

 * Uses solution from ilikenwf#114. Drop section in FAQs.
 * Update manpage.
 * Update copyright years.

Fix return value for clean command

Don't pipe downloader command through sed. Closes ilikenwf#140

 * Piping the downloader command will result in the downloader behaving
   like not in a terminal. This results in less nice output.

Fix aria checksum support with non-English locale. Closes ilikenwf#139

 * Additionally don't write checksum entry from apt to download file if
   aria doesn't know any checksums.

Fix source option. Closes ilikenwf#138

 * Fix typo in option detection introduced in 6355fd4 .