add ftps adapter, based on double_bag_ftps

[bxbd]

Not much to say about this, I needed to some special parameters for a certain deployment project, and fortunately this was pretty easy to accomplish since double-bag-ftps was just an extension on top of Net::FTP. So I just leapfrogged your original Dandelion::Adapter::FTP and replaced the ftp object it constructs. Also added a few config options to support it. Kudos for a building such a clean structure that facilitated this.

These config options got me to where i needed to be for this particular ftp server. but there may be more options required or better ways of articulating connection parameters (auth_tls, for example, maybe allowing user to pass in an arbitrary string would be better). i'm not really completely familiar with all the nuances of ftp encryption.

And, I hate to say, I'm not really familiar with ruby either, this is really my first foray. I only feel comfortable publishing this because the task was fairly trivial, and maybe it will be useful to others

[scttnlsn]

Awesome. Would you be willing to update the README with info about this new adapter?

[bxbd]

No problem, there you go, thanks for looking at it

[scttnlsn]

Great- thanks!