Merge pull request #1046 from stan-dev/bugfix/issue-866-vars-prefix

Fixes #866. Bugfix/issue 866 vars prefix
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
poisson_rng throws exception on lambda >= pow(2,30), along with modified
tests
Changed the definition of the upper bound for the mean, as suggested by
Bob
Lambda Upper bound = pow(2.0, 30.0)
Added poisson_log_rng for log-rate parameterized poisson, added tests for neg_binomial_2_rng, neg_binomial_2_log_rng, and neg_binomial_rng overflow exceptions
Merging develop into feature-1053-overflow-poisson-rng

Merge branch 'develop' of https://github.com/stan-dev/stan into bugfix/feature-1053-overflow-poisson_rng
Added poisson_log_rng documentation
removed unused tests, added constants for bounds, static cast vs. C casts, all for poisson
Merge branch 'develop' of https://github.com/stan-dev/stan into bugfix/feature-1053-overflow-poisson_rng

Merging Bob's commits
Merging documentation update into Bob's code review changes

Merge branch 'bugfix/feature-1053-overflow-poisson_rng' of https://github.com/stan-dev/stan into bugfix/feature-1053-overflow-poisson_rng
Updated documentation to include upper bounds for poisson_rng and neg_binomial_rng, etc.
Merge pull request #1098 from stan-dev/bugfix/feature-1053-overflow-poisson_rng

Bugfix/feature 1053 overflow poisson rng