Moved `inTemplate` initializer to appropriate place.
Added onToken support.
Added example for comments attachment.

* Fixed `onToken` & `tokenize` to return `startLoc` & `endLoc`
in token object only when `options.locations` is `true`.
* Fixed `onToken` tests.
* Added example for generating comments with escodegen.
Remove `copyToken` from acorn_loose (not needed anymore).