Bump version to 1.7.0

Bump version and bundle

Added fix by @kawamoto to the History doc.

Update bundler version in Gemfile.lock

Version bump.

Merge branch 'master' of github.com:DatabaseCleaner/database_cleaner

Bundled.

Bumped version.

DRY version number.

Merge pull request DatabaseCleaner#306 from DatabaseCleaner/release_1…

…_4_0

Release version 1.4.0