native-fetcher: fix to work with nginx 1.5.8+

nginx 1.5.8 changed the resolver api, which the native fetcher uses.

Fixes #578.

Squash-merge of @dinic's #581.
readme: release 1.7.30.2
release: prepare 1.7.30.3
Merge pull request #600 from pagespeed/huibao-prepare-release-1.7.30.3-beta

release: prepare 1.7.30.3
release: build against backported change
Merge pull request #635 from pagespeed/huibao-prepare-1.7.30.4-release

release: build against backported change
release: udpate version number 1.7.30.3 to 1.7.30.4
Merge pull request #636 from pagespeed/huibao-prepare-1.7.30.4-release

release: update version number 1.7.30.3 to 1.7.30.4
merge commit: merge 1.7.30.4 into master