compute_payments: Compute payment plan
In zamorarr/loanr: Helps calculate student loan repayment

Compute payment plan

1 2	compute_payments(balance, rate, ppm, years, plan = c("repaye", "ibr"), subsidized = FALSE, ppm_increase = 0)

`balance`	current balance or principal
`rate`	interest rate
`ppm`	student payment per month
`years`	number of years to calculate. Most debt forgiven after 25 years.
`plan`	which payment plan to use
`subsidized`	whether the government will help subsidze accrued interest
`ppm_increase`	how much to increase the monthly payment amount per year. This is done with the hopes that a student will get a good job and be able to pay more over time.