update docs for release 2.3.0

fix link to performance chart

release 2.2.0

switch to release 2.1.0 in gradle

prepare release 2.0.1

prepare release 2.0.0

update release version to 1.3.0

prepare for release 1.2.1

move isDoubleValue() to API changes, add performance regression

use project dependencies until big-math 1.1.0 is on maven central