TODOs for HTTP::Async

  * Add ability to pass in a file handle that will be used to store the
    content in. Aimed at people downloading large files that would otherwise
    fill up the memory. Could be done so that downloads greater than a certain
    size get sent to file rather than to memory. How to return this in the
    HTTP::Response though.

  * Do what is needed to get CPANTS tests to pass / run.

  * Fix the failing test case for Tatsuhiko Miyagawa.

  * Make sending non blocking - both the data and the initial DNS lookup.

  * Integrate the changes from Egor - set alarm to catch connection timeout.

  * Change max_redirects to max_redirect to be consistent with LWP::UserAgent

  * Add a max_content_size that will break connections if the content is to
    big - default is no limit.