[ADD] product_m2mcategories: migrated to new API
Fix Odoo version on Travis
product_gtin: port to v8
Rename badly-named variable: ean13_len -> ean_len
Small code simplification
Merge pull request #22 from alexis-via/8.0-port-product-gtin

product_gtin: port to v8
Merge pull request #21 from pedrobaeza/8.0-product_m2m_categories

[MIG] product_m2mcategories: Migrated to new API