Fix catch_failures option

If `:catch_failures => true` is supplied and no extra
`:acceptable_exit_codes` are supplied, a bug hindered the
`#apply_manifest_on` method from performing correctly.
Merge pull request #88 from hunner/fix_catch_failures

Fix catch_failures option
Add `:expect_failures` option

When performing positive tests of applying manifests, the
`#apply_manifest` method may be called with `:catch_failures => true`.

This commit also adds an argument of `:expect_failures` to allow
`#apply_manifest` to perform negative tests.
Merge pull request #89 from hunner/expect_failures

Add `:expect_failures` option