v.2.6.0

* custom pattern callback instead of imagedata

v.2.5.0

* color/background can be gradient (pass array of colors)
* color/background can be a custom pattern (pass image data)
* hash_equals prevent timing attacks

v.2.2.0

* support scale distortion vs position distortion
* add option(distortion_type)
* update tests

v.2.1.0 contd

* custom option(distortion) per difficulty

v.2.0.0, contd, fix some minor issues (JS,Py)

v.1.2.0

* math formula can rabdomly have multiplication factors
* image wave distortion depending on difficulty level

v.1.1.0 contd

* minor rendering adjustments

v.1.0.0 contd

* use plus or minus sign
* better text graphic measurement
* add reset method