Fix bug causing empty chef_export tarball

Due to shell expansion not being in effect when calling system with
array of arguments, the tarball w/ chef export ended up empty.

Pass a list of files to be archived as individual arguments instead
of a glob.
Do not move the exported file if tar fails
Remove revision from RoleObject, duplicates crowbar_revision
Rename revision -> crowbar_revision, fix call to role & sync check
Refactor incrementing crowbar revision to a separate method
Use crowbar_revision helper
Refactor increment_crowbar_revision and crowbar_revision in NodeObject
Merge pull request #1060 from bkutil/fix_export

Fix export
Fix i18n strings moved in #1059
Merge pull request #1067 from bkutil/fix_missing_translation

Fix i18n strings moved in #1059
Merge pull request #1065 from bkutil/proposal_revision_increments

Refactor revision increments
Run brakeman automatically in travis

As we're already including brakeman in our gem bundle, it'd be nice
to actually run it automatically.

When we're green w/ the vulnerabilities, we can turn on the -z option
and let the build fail on new ones.
Merge pull request #1071 from bkutil/add_brakeman_to_travis

Run brakeman automatically in travis
Switch rspec format to nested
Merge pull request #1076 from bkutil/use_nested_format_in_rspec

Switch rspec format to nested