make_dataset: Forms data set used for simulation
In rmsharp/stepwiser: Demonstrates effects of using stepwise variable selection

The data set is

1 2	make_dataset(n = 100, betas, corr, p, target_mean = 0, target_sd = 100, error_fun_mean = 1:10, error_fun_sd = 50:200)

`n`	number of observations
`betas`	coefficients used to form actual predictive variables
`corr`	correlations used in making predictive variables
`p`	number of predictive variables
`target_mean`	mean value of target variable
`target_sd`	standard deviation of target variable
`error_fun_mean`	vector of possible means used in the error function `error_fun`.
`error_fun_sd`	vector of possible standard deviations used in the error function `error_fun`