updated stan sub-repo
updating cmdstan to latest stan version
Merge pull request #62 from stan-dev/feature/issue-61-update-stan

Fixes #61. Feature/issue 61 update stan
updating git ignore
adding the right dependency for make
doc: updating doc
updating doc
including make/local from the makefile
doc: updating
updating stan to develop
Merge pull request #63 from stan-dev/feature/issue-22-manual-2.5

Fixes #22. Feature/issue 22 manual 2.5
updating doc
Merge pull request #65 from stan-dev/feature/issue-64-v2.5.0

Fixes #64. v2.5.0
updating stan to v2.5.0
removing doc
Merge pull request #67 from stan-dev/feature/issue-66-remove-built-doc

Fixes #66. Removes built doc for v2.5.0
updating to Eigen 3.2.2
removing make/local
Merge pull request #71 from stan-dev/feature/issue-68-remove-make-local

Fixes #68. removing make/local
Don't build or link against libstan.a since it's no longer needed.