Update .travis.yml to build docs in parallel.
Update .travis.yml
Adding --vanilla flag to Rscript call, removing python and perl dependencies.
Merge pull request #373 from stan-dev/feature/issue-369-makefile-shuffling

fixes #369.
removing generated doxygen and manual
Merge pull request #383 from stan-dev/feature/issue-381-remove-manual-from-repo

Fixes #381.
Merge pull request #242 from ido/patch-2

Update .travis.yml to build docs in parallel.
Merge branch 'develop' of https://github.com/stan-dev/stan into feature/parser_error_reporting