Update CI (webmozarts#103)

* sudo:false is deprecated
* gather coverage on php 7.3
* move hhvm/nightly builds to bottom of matrix
* test against php 7.4 snapshot, but allow it to fail
* remove prefer lowest flasgs
* simplify xdebug disabling

.travis.yml

@@ -1,7 +1,5 @@
 language: php
 
-sudo: false
-
 branches:
   only:
     - master
@@ -14,28 +12,28 @@ matrix:
   include:
     - php: 5.3
       dist: precise
-    - php: 7.1
-      env: COVERAGE=yes
     - php: 5.4
     - php: 5.5
     - php: 5.6
     - php: 7.0
-    - php: hhvm
-    - php: nightly
     - php: 7.1
-      env: COMPOSER_FLAGS='--prefer-lowest --prefer-stable'
     - php: 7.2
     - php: 7.3
+      env: COVERAGE=yes
+    - php: 7.4snapshot
+    - php: hhvm
+    - php: nightly
   allow_failures:
+    - php: 7.4snapshot
     - php: hhvm
     - php: nightly
   fast_finish: true
 
 before_install:
-  - if [[ $TRAVIS_PHP_VERSION != hhvm && $TRAVIS_PHP_VERSION != 7.3 && $COVERAGE != yes ]]; then phpenv config-rm xdebug.ini; fi;
+  - if [[ $COVERAGE != yes ]]; then phpenv config-rm xdebug.ini || true; fi;
 
 install:
-  - composer update $COMPOSER_FLAGS --prefer-dist --no-interaction
+  - composer update --prefer-dist --no-interaction
 
 script:
   - if [[ $COVERAGE = yes ]]; then vendor/bin/phpunit --coverage-clover=coverage.clover; else vendor/bin/phpunit; fi