Allow custom file to be deployed

[jonpither]

Hi,

Beanstalk now optionally takes ZIPs containing a Dockerfile. The coupling of building WARs and deployment in the deploy task in lein-beanstalk is an issue for this approach.

I built a little lein plugin to wrap lein-beanstalk to facilitate uploading custom files and it works OK:

https://github.com/juxt/lein-dockerstalk/blob/master/src/leiningen/dockerstalk.clj

TBH I'm not sure how you would change lein-beanstalk, looking at the current code. The deploy task already takes a couple of args (a project and an env name). Perhaps adjust this to be variadic key/value args and take a simple 'path' parameter, and if this is present then we don't build the uberwar and use the filename from this? This would be a breaking change though.

Be interested to hear your thoughts. I'd like to decommission the plugin I built in favour of using lein-beanstalk if possible.