BUGFIX: Remove failing package installation of 'zip'

Closes #33

See merge request !34

TASK: Provide file doc inline headers to all files

Closes #37

See merge request !33

TASK: Adjust documentation for new composer package type

Closes #34

See merge request !31

FEATURE: Implement PSR-2 PHPCodeSniffer Standard

Closes #28

See merge request !25

Feature/integrate psr2 into ci

See merge request !29

Feature/refactor code

See merge request !30

* As we can use returns instead of local variable.
* This will make it easier to see the return value of the method.

* Do not use else, as hinted by phpmd, use return instead.

* Remove duplicate empty line.
* Sort namespace imports alphabetical.

* Move before_script to be executed for all, also new job. This way
  dependencies are installed.
* Create target folder for reports. Otherwise reports can not be
  written.
* Use tetraweb image, as it already provides composer.

Relates: #28

Relates: #28

FEAUTRE: Provide a basic documentation

Closes #8

See merge request !27

FEATURE: Provide branch alias

Closes #31

See merge request !28

FEATURE: Gitlab ci initialized (including phpunit test)

Closes #25

See merge request !26

TASK: Rename primary composer plugin type

Closes #24

See merge request !24

# Conflicts:
#   README.md

TASK: Remove travis-ci configuration

Closes #26

See merge request !23

Readded old composer package type `php-codesniffer-standards`.
Will be removed before the first stable release.

Added `phpcodesniffer-standards` (plural) as also supported
composer package type.