delete testing/filetesting; use github.com/testing/filetesting instead
sortimports
Merge remote-tracking branch 'origin/master' into 003-remove-filetesting

Conflicts:
	utils/zip/zip_test.go
	worker/uniter/charm/manifest_deployer_test.go
	worker/uniter/relationer_test.go
	worker/uniter/uniter_test.go
Merge remote-tracking branch 'origin/master' into 003-remove-filetesting
Merge pull request #31 from rogpeppe/003-remove-filetesting