update to archiver v0.9, drop support for node 0.8, test on .11

Closes gh-106.
0.9.0
update readme
allow directories to pass-through to archiver.
use `filter` property to filter them out.

Closes gh-107.
0.9.1
Merge remote-tracking branch 'origin/master' into gzip_min_length

Conflicts:
	README.md
	test/compress_test.js
Added "gzipMinLength"