Update plugin version to 1.8.1. (WordPress#3720)

Update version to 1.8. (WordPress#3694)

Bump version to 1.7. (WordPress#3479)

Bump version to 1.6.1. (WordPress#3309)

Bug fixes.

Update version to 1.6. (WordPress#3254)

Bump version to 1.5.2

Bump version to 1.5.1. (WordPress#3123)

Bump plugin version to 1.5.0 (WordPress#3097)

Bump version to 1.4.0. (WordPress#2954)

Bump version to 1.3. (WordPress#2875)