Make slugs required for module stubs
Added tests for axes properties in dashboard stubs
Override module schema for specific edge cases
Validate submodules inside tabs according to the same schema as top level modules
Added a basic jshintrc to schema dir
Switch dev config to point to preview

Most development is happening outside of the dev vm so we should point
to preview rather than expecting services to be running locally.
Merge pull request #401 from alphagov/feature/json-schema-testing

Improve json schema for modules
Merge pull request #402 from alphagov/change-dev-config

Switch dev config to point to preview
Set tabular numbers only where numbers align vertically – tables and graph y-axes