First draft of updating products purly on SKU. Refs #67.
Merge branch 'master' into variant-update
Add test case for product building incl. failure of missing product type.
Merge branch 'master' into variant-update
Remember correct rowIndex per variant. Refs #67.
Update TODO.
Fix arrow type.
Use underscore functions.
Fix typo and add missing require.
Merge pull request #68 from sphereio/variant-update

Variant update