Implement tests using unittest completely

For some reason `nosetests` doesn't run the generated tests so I changed the build command for travis
Fix order of packages

(also includes a small tweak for SublimErl)
Add tests for the order of packages
Add "description" to the accepted keys for packages
Add tests for the order of repositories in channel.json
Further improve tests

- Add optional tests for all repositories in channel.json (after downloading all of them).
- Add tests for "date" property in releases (only tested with custom repos)
- Allow "-x32" and "-x64" prefixes for "patforms"
Fix package order
Merge pull request #1669 from wbond/better_tests

Better tests