Moved diff dependency to external lib. Standardized some of the code style
Diff dependency moved to composer fork
Added explicit enabling/disabling and framework name fallback

You can now use the normal package name as the framework name,
which is probably preferential, but you will have to explicitly enable
Opus support via `extra.opus.enabled`.

For backwards compatibility, if you define a framework name
explicitly Opus will be considred enabled unless overloaded by
`extra.opus.enabled` to be false.

README updated to reflect this.