filetesting: create file with correct mode; test failures are annotated
Merge pull request #14 from rogpeppe/filetesting-improvements

filetesting: create file with correct mode; test failures are annotated
Add test for suite level value restoration.

When a value is modified in a test through patch value
check that the suite level value is restored when the
test is torn down.
Merge branch 'master' of https://github.com/juju/testing into suite_level_patch_restore