Merge pull request #578 from dajiaji/bump-to-v2_8_0

Bump version to 2.8.0.

Merge pull request #542 from dajiaji/bump-to-v2_7_5

Bump version to 2.7.5.

Merge pull request #498 from dajiaji/bump-to-v2_7_4

Bump version to 2.7.4.

Merge pull request #481 from dajiaji/bump-to-v2_7_3

Bump version to 2.7.3.

Merge pull request #472 from dajiaji/bump-to-v2_7_2

Bump version to 2.7.2.

Merge pull request #468 from dajiaji/bump-to-v2_7_1

Bump version to 2.7.1.

Merge pull request #453 from dajiaji/bump-to-v2_7_0

Bump version to v2.7.0.

Merge pull request #437 from dajiaji/v2_6_0

Bump version to v2.6.0.

Merge pull request #434 from dajiaji/v2_5_1

Bump version to v2.5.1.

Merge pull request #431 from dajiaji/bump-to-v2_5_0

Bump version up to v2.5.0.