Update dependencies for PHP 8

.travis.yml

@@ -8,11 +8,12 @@ matrix:
     - php: "7.1"
     - php: "7.2"
     - php: "7.3"
-    - php: "7.4snapshot"
+    - php: "8.0"
     - php: "nightly"
   allow_failures:
     - php: "nightly"
-    - php: "7.4snapshot"
+    - php: "7.4"
+    - php: "8.0"
 
 install:
     - composer self-update

composer.json

@@ -40,8 +40,8 @@
     "php": "^7|^8"
   },
   "require-dev": {
-    "phpunit/phpunit": "^6|^7",
-    "vimeo/psalm": "^1|^2|^3"
+    "phpunit/phpunit": "^6|^7|^8|^9",
+    "vimeo/psalm": "^1|^2|^3|^4"
   },
   "autoload": {
     "psr-4": {

phpunit.xml.dist

 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="true"
-         backupStaticAttributes="false"
-         bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnError="false"
-         stopOnFailure="false"
->
-    <testsuites>
-        <testsuite name="Constant Time Encoding Test Suite">
-            <directory suffix="Test.php">./tests</directory>
-        </testsuite>
-    </testsuites>
-    <filter>
-        <whitelist processUncoveredFilesFromWhitelist="true">
-            <directory suffix=".php">./src</directory>
-        </whitelist>
-    </filter>
-</phpunit>
\ No newline at end of file
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="true" backupStaticAttributes="false" bootstrap="vendor/autoload.php" colors="true" convertErrorsToExceptions="true" convertNoticesToExceptions="true" convertWarningsToExceptions="true" processIsolation="false" stopOnError="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
+  <coverage processUncoveredFiles="true">
+    <include>
+      <directory suffix=".php">./src</directory>
+    </include>
+  </coverage>
+  <testsuites>
+    <testsuite name="Constant Time Encoding Test Suite">
+      <directory suffix="Test.php">./tests</directory>
+    </testsuite>
+  </testsuites>
+</phpunit>