Modernize plugin

Hi,

I just made an ember-addon named [ember-cli-yuidoc](https://github.com/cibernox/ember-cli-yuidoc) and I had to update broccoli-yuidoc to make it performant.

Now it uses the latest version of all broccoli-plugins available, so it has symlinking and everything new broccoli. Is faster that it used to be.

The bad part is that the semantics of `CachingWriter` have changed a lot, so this has breaking changes. This must bump version number a middle digit at least.

I would love feedback, and eventually, pushing to npm :)