Various improvements

[simonhamp]

Hi Will, as you can probably tell from this PR I've been going around with this package for a bit. I'd really like to just push forward with one package rather than publicise my fork.

I appreciate this may seem like a daunting PR to review. Happy to work through it with you, but the main changes are:

• Simplified the composer dependencies to those that are actually in use. This will make setting up dev environment speedier and lighter
• Gotten rid of some files that seemed a bit superfluous and generally tidied the package up, renaming some of the main classes to help better identify their purpose
• Attempted to make the core console command more flexible and readable - it's now possible to use ZeroMQ with any server type (not just WAMP)
• Simplified the readme to make getting started simpler for newbies
• Requiring PHP 7.1+

You'll probably notice references to laravel-zmq - please ignore all of this, I've since removed it.

Final note is that this all is most definitely a breaking change that will stop backwards compatibility. So I recommend that you tag a new major release if you merge these changes.

Any issues or questions, let me know and I will try to resolve.

[gcphost]

Looks good