Treat '--speclj' as an alternative help option

My attempt at tackling #102. 

I wanted to remove the "help" option altogether, but didn't want to risk deprecating existing functionality. Given that Leiningen hijacks the "help" flag, is there another way that it could be used? If not, then we can kill it.

It's also worth mentioning that according to [Leiningen's plugin docs](https://github.com/technomancy/leiningen/blob/master/doc/PLUGINS.md) you should be able to attach `^:pass-through-help` metadata to your defined task to implement this workaround; this didn't work for me for some reason.