@command plugin

I've done some work here to use the `@command` decorator. Doing so will simplify a lot of the regex logic that's currently in the plugin and make it a bit simpler to handle arguments. Also, this will let users do either `helga thanks foo` or `!thanks foo`, where the '!' prefix is something globally configurable in helga settings.

I made some specific tests for all of the individual methods, so these are probably duplicating the contents of test_integration.py in some respect, but that might not be so terrible in the end.

I've also bumped the version up to 1.0.0 as some of the commands are changed quite a bit (i.e. `helga karma alias nick1 nick2`)