function handleEditorChange(session, document, previousDocument) {

        if (!currentModule) {
            currentModule = new TernModule();
        }
        
        return currentModule.handleEditorChange(session, document, previousDocument);
    }
Called each time a new editor becomes active.

@param {Session} session - the active hinting session
@param {Document} document - the document of the editor that has changed
@param {?Document} previousDocument - the document of the editor is changing from