Merge pull request yahoo#512 from yahoo/leewyang_v2.2.1

v2.2.1 release

Merge pull request yahoo#504 from yahoo/leewyang_v2.2.0

v2.2.0 release

Merge pull request yahoo#497 from yahoo/leewyang_v2.1.3

prepare v2.1.3 release

Merge pull request yahoo#491 from yahoo/leewyang_v2.1.2

v2.1.2 release

Merge pull request yahoo#489 from yahoo/leewyang_v2.1.1

v2.1.1 release

Merge pull request yahoo#484 from yahoo/leewyang_v2.1.0

prepare v2.1.0 release

Merge pull request yahoo#458 from yahoo/experimental

TensorFlow 2.0 compatibility

Merge pull request yahoo#457 from yahoo/leewyang_v1.4.4

v1.4.4 release

Merge pull request yahoo#409 from yahoo/leewyang_v1.4.3

v1.4.3 release

Merge pull request yahoo#389 from yahoo/leewyang_v1.4.2

v1.4.2 release