add nightly, update 7.4, use bionic

.travis.yml

@@ -1,39 +1,39 @@
 language: php
-dist: xenial
+
+dist: bionic
 
 cache:
   directories:
-    - $HOME/.composer
-    - vendor
+  - $HOME/.composer
+  - vendor
 
 git:
   depth: 5
 
 php:
-  - 7.2
-  - 7.3
-  - 7.4snapshot
-  - nightly
+- 7.2
+- 7.3
+- 7.4
+- nightly
 
 env:
   matrix:
-    - COMPOSER_FLAGS="--prefer-lowest"
-    - COMPOSER_FLAGS=""
+  - COMPOSER_FLAGS="--prefer-lowest"
+  - COMPOSER_FLAGS=""
 
 matrix:
   fast_finish: true
   allow_failures:
-    - php: nightly
-    - php: 7.4snapshot
+  - php: nightly
 
 before_install:
-  - travis_retry composer self-update
+- travis_retry composer self-update --no-interaction
 
 install:
-  - travis_retry composer update --no-interaction --no-progress --prefer-dist $COMPOSER_FLAGS
+- travis_retry composer update --no-interaction --no-progress --no-suggest --prefer-dist $COMPOSER_FLAGS
 
 script:
-  - vendor/bin/phpunit --coverage-text --coverage-clover coverage.xml
+- vendor/bin/phpunit --coverage-text --coverage-clover coverage.xml
 
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+- bash <(curl -s https://codecov.io/bash)