fix: update to work with Karma 0.11

Since Karma executes immediately, we don't have all the browsers in advance, the reporter has to listen on browser_start instead.
chore: inc version

NPM when fetching from this github branch does check the version and sees it's the same it already has in the cache and does not install this branch.
feat: add a default config

So that we can remove it from the default Karma config in karma/config.js.
refactor: use onExit rather than explicit emitter
feat: normalize the outputFile path

We used to this in Karma's config, but it really belongs here.
refactor: remove unused var
fix: Compatibility with Karma 0.10

Since 9e3191c4c51139fd46117eb7fcc50d4bcf6b457b this reporter has only been working with Karma 0.11, which causes all kinds of version mismatch troubles. It's easy to support both versions, so let's do it.