* tests: update to PHPUnit 6.0 with rector
* [cs] clean empty docs
* composer: bump to PHPUnit 6.4
* tests: use class references over strings
* cleanup
* travis: move coveralls here, decouple from package
* composer: use PSR4
* phpunit: simpler config
* travis: add ecs run
* composer: add ecs dev
* use standard vendor/bin directory for dependency bins, confuses with local bins and require gitignore handling
* ecs: add PSR2
* [cs] PSR2 spacing fixes
* [cs] PSR2 class name fix
* [cs] PHP7 fixes - return semicolon spaces, old rand functions, typehints
* [cs] fix less strict typehints
* fix typehints to make tests pass
* ecs: ignore typehint-less elements
* [cs] standardize arrays
* [cs] standardize docblock, remove unused comments
* [cs] use self where possible
* [cs] sort class elements, from public to private
* [cs] do not use yoda (found less yoda-cases, than non-yoda)
* space
* [cs] do not assign in condition
* [cs] use namespace imports if possible
* [cs] use ::class over strings
* [cs] fix defaults for arrays properties, properties and constants single spacing
* cleanup ecs comments
* [cs] use item per line in multi-items array
* missing line
* misc
* rebase
* Remove user-specific gitignore
* Add return type hints
* Avoid global namespace in docs
* Rename rules -> getRules
* Split up rule generation
Todo:
* Move set theory out to math
* Extract rule generation
* Generating frequent k-length item sets
* Generating rules based on frequent item sets
* Algorithm has exponential complexity, be aware of it
* Apriori algorithm is split into apriori and candidates method
* Second step rule generation is implemented by rules method
* Internal methods are invoked for fine grain unit tests
* Wikipedia's train samples and an alternative are provided for test cases
* Small documentation for public interface is also shipped
