Refactor test code, add test theme and fix tests.

.travis.yml

modules/ui_patterns_test/ui_patterns_test.info.yml

tests/features/overview.feature

tests/features/setup.feature

tests/src/PhpUnit/UiPatternsManagerTest.php

tests/target/composer.json

tests/target/composer.lock

tests/target/custom/ui_patterns_test/composer.json

...m/ui_patterns_test/config/install/system.theme.global.yml

...t/custom/ui_patterns_test/config/install/system.theme.yml

...om/ui_patterns_test/templates/pattern--pattern1.html.twig

...om/ui_patterns_test/templates/pattern--pattern2.html.twig

...get/custom/ui_patterns_test/ui_patterns_test.features.yml

.../target/custom/ui_patterns_test/ui_patterns_test.info.yml

...s/target/custom/ui_patterns_test/ui_patterns_test.install

.../custom/ui_patterns_test/ui_patterns_test.ui_patterns.yml

tests/target/custom/ui_patterns_test_theme/composer.json

...patterns_test_theme/templates/custom-theme-hook.html.twig

...om/ui_patterns_test_theme/ui_patterns_test_theme.info.yml

ui_patterns.module