Add PHPStan 1.0 compatibility (#25)

* Add PHPStan 1.0 compatibility

* Replace usage of deprecated Broken with ReflectionProvider

Add docker image and dockerized dev tools (#10)

* Add Makefile with dockerized dev tools

* Add Makefile with dockerized dev tools

* change composer installation: use latest version

* Up php version for base docker image

* Add to readme info about development installation with(-out) docker

* Review fixes:
- quotes around phpunit args
- use php 7.1 for image
- remove unused volumes mounting for composer
- clean apt-get lists

Reorder RUN instuctions for best layers caching, remove unused packages.

* Fix PATH addition

* Fix dockerized tools

* readme cs fixes

* Fix dockerfile lints

* Fix lint: quote paths

* Disable some dockerfile lint rules

* bash quotes

Co-authored-by: n.gnato <[email protected]>

Fix lint: remove blank line (#19)

Fix badge

Merge pull request #15 from JeroenVanOort/php-8

Added compatibility with PHP 8

Added phpstan 0.12.33+ compatibility (#14)

Update PHPStan from 0.11 to 0.12 (#11)

* Update PHPStan from 0.11 to 0.12

* Fix PHPunit tests

Merge pull request #9 from shadowhand/patch-1

Add support for extension-installer