fixed gunzip error

It seems here the chunks need to be unzipped as they come in and not at the end. the commited code seems to fix the errors. Refer to http://stackoverflow.com/questions/10207762/how-to-use-request-or-http-module-to-read-gzip-page-into-a-string for my solution @rcrichton please review
This on data event isn't used when with 'gzip' responses. So maybe we should only do the gunzip on data if the content is of type gzip. Else we are storing the response twice in memory. (1 in bufs the other in uncompressedBody).