chore(ci): test against PHP 7.4

* Updated to test again PHP 7.4 and to use that for coverage reporting.
* Added PHP nightly builds as an allowable failure.
* Added a git ignore as well as a `phpunit` configuration.
* Updated the tests and CI configuration to better handle the juggling of PHP and `phpunit` versions.
* Updated the coveralls dependency to be the latest and greatest instead of the deprecated package.
* Tweaked the README, updated the LICENSE years and bumped this package's version.
* Dropped Patreon link in favor of using Github Sponsors.

.travis.yml

@@ -14,27 +14,27 @@ matrix:
       dist: trusty
     - php: 7.0
       dist: xenial
-      env: PHPUNIT=5.7
     - php: 7.1
     - php: 7.2
     - php: 7.3
+    - php: 7.4
+      env: COVERAGE=true
+    - php: nightly
+  allow_failures:
+    - php: nightly
 
 install:
+  - php --version
   - composer install
-  - if [[ $PHPUNIT == 5.7 ]]; then composer require "phpunit/phpunit:5.7"; fi
 
 before_script:
   - mkdir -p build/logs
-  - cd tests
 
 script:
-  - |
-    if [[ $PHPUNIT == 5.7 ]]; then
-      ../vendor/bin/phpunit --colors --coverage-clover ../build/logs/clover.xml .
-    else
-      phpunit --colors --coverage-clover ../build/logs/clover.xml .
-    fi
+  - vendor/bin/phpunit --coverage-clover build/logs/clover.xml
 
 after_success:
-  - cd ..
-  - php vendor/bin/coveralls --config .coveralls.yml -v
+  - |
+    if [[ $COVERAGE ]]; then
+      travis_retry php vendor/bin/php-coveralls --config .coveralls.yml -v
+    fi