CRAN version 2.0.0

Bump to version 2.0.0 due to large number of changes, some visible to user, while some are due to submission to rOpenSci review. From the NEWS file:

• Added a progress bar for run_mcmc.
• Added a fitted method for extraction of summary statistics of posterior
  predictive distribution p(y_t | y_1, ..., y_n) for t = 1, ..., n.
• Rewrote the summary method completely, which now returns data.frame. This
  also resulted in some changes in order of the function arguments.
• The output of predict method is now a data frame with column weight
  corresponding to the IS-weights in case of IS-MCMC. Previously resampling
  was done internally, but now this is left for the user if needed
  (i.e. for drawing state trajectories).
• The asymptotic_var and iact functions are now exported to users, and they
  also contain alternative methods based on the posterior package.
• New function estimate_ess can be used to compute effective sample size
  from weighted MCMC.
• Added compatibility with the posterior package by defining as_draws
  method for converting run_mcmc output to draws_df object.
• New function check_diagnostics for quick glance of ESS and Rhat values.
• Large number of new tests, and improved documentation with added examples.
• Large number of internal tweaks so that the package complies with
  goodpractices package and Ropensci statistical software standards.