2.0 updates

[redthor]

Suggested updates:

1. Minimum php is 7.1 - update travis yml
2. Drop antimattr/test dependency
3. Update phpunit to 7 (see Update phpunit to 6 or 7 #20)
4. Switch to [ ] array syntax
5. MongoDB Adapter:
   1. Firstly, add "alcaeus/mongo-php-adapter" as a dependency
   2. Secondly, look at removing usage of mongo-php-adapter by using MongoDB base classes
6. Set up code quality tool Set up automated code quality tool #23

Complete the changes for the bundle too https://github.com/doesntmattr/mongodb-migrations-bundle

[redthor]

@trq @caciobanu - good to hear your thoughts.
Some comments in #21 relate to this.

Thanks.

[caciobanu]

For number 5 I think that going with the official library from MongoDB https://github.com/mongodb/mongo-php-library would be a better choice as the new Doctrine ODM will use that directly. That would help us integrating the bundle with the new ODM.

[redthor]

It turns out that the library uses Doctrine classes exclusively (apart from some unit tests). So the adapter wasn't really required. See the changes in #30

^^ wrong. There's the \MongoTimestamp used in Version. The tests mock it so it doesn't appear to error when unit tests run..? I'll need to look into how to avoid using that class.

[redthor]

#30 should close this, and we can test against dev-master locally then create the release.

[redthor]

I've tested against dev-master - good to go on the release.