Be able to download the app without running it

[anaisbetts]

afaik I didn't see a way to do everything but run without actually running the executable (I want to call path(), then call spawn aka run the app but with stdio piped etc etc), it'd be cool if there was a fetch method that guarantees that path will work (I used bin-wrapper to wrap the Google protoc compiler, https://github.com/anaisbetts/protoc-bin)