Merge branch 'release/0.1.4'
Merge branch 'release/0.1.5'
Merge branch 'develop'
Merge branch 'release/0.1.6'
Merge branch 'release/0.2.0'
Merge branch 'release/0.2.1'
add trigonometric operations.
Merge branch 'master' into develop
update version
add documentation examples for trigonometric features
Merge branch 'release/0.2.2' into develop