v1.3.9

TL;DR

• The first release after splitting the bundle to be a standalone package with its own release cycle.

Details

• #3 Set up Travis CI (@pamil)
• #10 Set up Travis CI for 1.1 (@pamil)
• #11 Organise code into directories (@pamil)
• #12 Add PHPStan to the build (@pamil)
• #13 Clean up PHPUnit tests a bit (@pamil)
• #14 Add SyliusLabs/CodingStandard (@pamil)
• #15 Test against Symfony 3.4., 4.1. and 4.2.* (@pamil)
• #16 Refreshed docs & readme (@pamil)