loadScript in the Node executor shouldn't always use path.resolve

[jason0x43]

In Node#loadScript, modules are loaded with require(path.resolve(script)). This allows script paths in the intern config to be relative to the project root. However, it breaks resolution for normal Node modules (e.g., if script were something in node_modules). Intern should handle this situation, as well. The naive solution would be to just do something like:

try {
    require(path.resolve(script));
} catch (error) {
    require(script);
}

[jason0x43]

Intern may also need to take the path of the intern.json file itself into account. This could allow it to load modules relative to the config, which would be relevant if the config were itself contained in a node module that had a nested node_modules directory.

project
    node_modules/
        tester/
            intern.json        <--- requires 'test-extras'
            node_modules/
                test-extras/