v0.3.18 Bug fix release for binary offsets

Fix for incorrect offset for string/variable list columns as reported in #720 (comment)

Thanks @lucazanna for the feedback!

What's Changed

• Train OPQ and write rotation matrix to index file by @eddyxu in #713
• removing warnings by @gsilvestrin in #721
• [Bug] Fix IVF merge sort when refine factor is presented. by @eddyxu in #722
• Add input / output schema contract to Global Take by @eddyxu in #728
• Fix offsets for Binary/Lists/LargeLists by @gsilvestrin in #727

Full Changelog: v0.3.17...v0.3.18