Fixed https://github.com/danwrong/restler/issues/112

Fixed bug described in https://github.com/danwrong/restler/issues/112 by creating a new EventEmitter for each Request instead of using the same shared EventEmitter prototype (which uses, what amounts to, a 'static' _events array.

Signed-off-by: Steven Wright <swright@ripplingcreek.com>