Merge pull request #1 from philouc/AR-noise-TrueDev

Ar noise true dev
Simulation AR noise
Merge branch 'AR-noise-TrueDev' of https://github.com/ainafp/pyhrf into AR-noise-TrueDev

Phil and Aina changed files separately.
fixed AR noise
Merge pull request #2 from ainafp/AR-noise-TrueDev

Ar noise true dev