Schemavalidator

Bugfixes

Make id's in subdirs relative to main directory.
A schema in `sub/test.json` has `id` `sub/test.json`. This makes relative paths and id's interchangeable.

Add support for schemas in sub directories
- Schemas in directories that are children of the `schema_base_path`
directory are now also found and parsed. You can use `"$ref":
"subdir/schema.json"` to refer to these schemas.
- `id` field value now has to be identical to file_name, as we're now
indexing the schemas by `[subdir/]file_name` instead of `id`.
- Dropping support for `Python 3.4`. So we can use the recursive feature
of `glob`.

First beta release