Simplified the reporter API and added support for third-party reporters

[patrick-steele-idem]

I removed the need for reporters to inherit from Base and moved all of the static methods that were part of Base into the utils module. The Runner now collects the common stats (# of suites, # of benches and elapsed time) and passes the stats to the reporter as the argument to the end event listeners. Each reporter now is simply a module that exports a function of the following form:

module.exports = function(runner, utils) {
}

Lastly, I added support for using third-party reporters. Third-party reporters can either be installed via npm in the user's project or they can be referenced using a relative path that is considered relative to process.cwd(). For example:

matcha templating-benchmarks.js --reporter ./my-custom-reporter

Thanks for creating this module! I found it very helpful when building templating benchmarks: https://github.com/raptorjs3/templating-benchmarks

I wanted to be able to easily report additional information--hence the need for this Pull Request.

--Patrick

[logicalparadox]

thanks, looks great!

[logicalparadox]

Release in 0.5.0. Also, gave you push access to GH repo. Your contribution and usage warrants first class access. Please email me via my GH profile so that I have your email should I need to contact you directly in regards to this repo. Thanks!