incrementing version number to 2.1.0
adding artifacts (manual + api doc) to the repository for v2.1.0
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Add some more API documentation to LDLT_factor and LDLT_alloc.
fixes issue #464
added diag_post_multiply to signatures and tested compilability
Merge pull request #461 from stan-dev/release/v2.1.0

Release/v2.1.0
Revert "adding artifacts (manual + api doc) to the repository for v2.1.0"

This reverts commit cb8a91067d40ed64793aa88ad3ffefadbe665ce2.
Merge pull request #466 from stan-dev/release/v2.1.0

release/v2.1.0
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
moved math tests to src/test/unit/math
moved mcmc tests to src/test/unit/mcmc
cleaning up mcmc tests
moved memory test to src/test/unit/memory
moved meta test to src/test/unit/meta
moved model test to src/test/unit/model
moved prob tests to src/test/unit/prob
moved models tests to src/test/CmdStan/models
disabled 5 model tests that have failed for v2.1.0
switched to arena malloc to fix #472