Various code tightup

Merge pull request #221 from PyFE/basket

Various changes / Clean up

heston model propereties added

Merge pull request #205 from PyFE/opt_abs

All changes so far

Model class refactoring

Defined xxxParams class for each model type and used them for defining models.

Ousv Benchmark Data update

Merge pull request #200 from PyFE/ousv

Update ousv_benchmark.xlsx

Class name change

New release for OUSV.

v0.3.2: Update pyproject.toml

New version after migrating to project.toml and version automation

PyFENG 0.3.0

Updates so far.

PyFENG 0.2.4

Updates so far

PyFENG 0.2.3

Merge pull request #141 from PyFE/heston-mc

Various changes in the SV/SABR models.

PyFENG 0.2.2

Include Excel data files for reference parameter sets