Merge branch 'develop' of https://github.com/stan-dev/stan into develop
alphabetized function_signatures.h
renaming stan::math::epsilon() to stan::math::machine_precision()
removing undoced functions from function signatures
removing commented block
added citations, checked format
Merge branch 'develop' of https://github.com/stan-dev/stan into feature/issue-187-citations
Merge pull request #274 from stan-dev/feature/issue-248-functions

Fixes #248. remove function signatures for undoc'ed functions
Merge pull request #277 from stan-dev/feature/issue-187-citations

Fixes #187. Updated citations
Merge branch 'develop' into feature/issue-246-website