Fix handling of execpath/execPath

Externally execPath makes more sense, but execpath is the convention
followed by strong-service-upstart for compatibility with other
templates.
Change --version to --upstart

Using --version makes no sense when support for other inits is on the
roadmap. This should pave the way for hypothetical options like
--systemd or --launchd or --sysvinit.
Bump strong-service-upstart dependency
1.0.0