Fix python2.7 support.
Fix to work with current eve version.
Add flake8 lint to travis ci.
Remove unused package.
Disable linting of features files.
Merge remote-tracking branch 'petr/master'
Add missing item properties.
Archive all related items when archiving type:composite.
Set eve version to last commit.
Allow description_text to be nullable.
Refactor signals/datalayer into separate modules.
Move tests inside superdesk module.
Allow using local file system storage for uploads.

Introduce new config - DEFAULT_FILE_STORAGE - which you can use to
change class used for storing binaries.

Also refactor tests to be able to change config per test.
Fix subject name parsing.

Try to find name, if not presented use literal value.
Add sessions resource with sessions for last 12h.
Implement user_roles endpoint.
Check permissions if user has assigned user role.
fix(datalayer): Add missing find parameter in find_all
fix(io.newsml): Fix xml parsing

Use same way of parsing xml when testing to get
the same errors like when fetching it via api.
Change the way permissions are stored per role.

Instead of a list it's a dict now, eg:

```
{
    "permissions": {
        "ingest": {
            "get": 1
        },
        "archive": {
            "post": 1
        }
    }
}
```