rstantools v1.2.0

rstantools 1.2.0

• Minor fixes to rstan_package_skeleton for better Windows compatibility. (#1, #2)
• Fix some typos in the developer guidelines vignette. (#3, #4)
• Add loo_predict, loo_linpred, and loo_predictive_interval generics (in
  preparation for adding methods to the rstanarm package). (#5)