Use pre-compiled Stan models

Compile Stan models at compile time.

Insist on rstan 2.14.1

Update rstan requirement to 2.14.1 to avoid bug: http://andrewgelman.com/2017/01/01/stan-2-14-released-r-python-fixes-bug-sampler/

Improve sparse approximation

• Increase border of inducing points in sparse approximations
• Fix further Stan bug (feature?) with square root of integers
• Update rstan requirement to 2.12.1 from bad 2.10 version: http://andrewgelman.com/2016/07/31/stan-2-11-good-stan-2-10-bad/

v1.2.3

Update for new package versions: rstan (2.10.1) and dplyr (0.5.0).

For manuscript revision

Changed cell size normalisation strategy in scripts.