modelStudio v1.1.0

• rename modelStudioOptions() to ms_options()
• add new ms_update_options() function that updates the options of a modelStudio object
• add new ms_update_observations() function that updates the observations of a modelStudio object
• lower B default value from 15 to 10 and N default value from 400 to 300
• feature_importance is now calculated on 10*N sampled rows from the data
• use ranger instead of randomForest everywhere
• remove unnecessary imports, update the documentation
• added auto_unbox = TRUE to jsonlite::toJSON and changed the .js code to comply
• add new class "modelStudio" to the modelStudio() output