v0.5.0 CRAN release

Implements both bug fixes and new features:

ordbetareg v0.5.0

• Fixed bug disabling extra priors for phi regression/modeling.
• Added pp_check_ordbetareg function for accurate posterior predictive plots for discrete and continuous outcomes.
• Updated vignette and documentation.

ordbetareg v0.3.0

• Fixed bugs relating to processing of bounded outcomes.
• Allow for user-specific bounds to be set for normalization of outcome to 0/1 (issue #2).
• Enable multiple imputation and multivariate responses with brms.
• Fix documentation issues (issues #4 and #5).