Add an alternative way of implementing Tauchen's method to make_tauchen_ar1()

[QingyuanFang]

Qingyuan: I closed Pull requests #1409 and initiate this new one.

Please ensure your pull request adheres to the following guidelines:

• Tests for new functionality/models or Tests to reproduce the bug-fix in code.
• Updated documentation of features that add new functionality.
• Update CHANGELOG.md with major/minor changes.

[QingyuanFang]

@llorracc @mnwhite

Because there have been many changes to HARK since pull request #1409 was made (for instance, restructuring of "distribution.py" into a folder), I closed the original pull request and initiate this new one.

Many thanks.