Upgrade to TestFrameworkAdapter 0.3.0 (#1)

- Upgrade
- Correct the platform config in the `composer.json`: we want a PHP version constraint not a platform config
- Remove 7.2 compatibility
- Ignore the `build` artefact file generated from running `make`

Author: theofidry

.gitignore

@@ -3,4 +3,5 @@
 /.idea
 /.php_cs.cache
 /vendor/
-infection.log
+/infection.log
+/build/

.travis.yml

@@ -1,6 +1,5 @@
 language: php
 php:
-  - 7.2
   - 7.3
   - 7.4
   - nightly

composer.json

@@ -23,13 +23,11 @@
         ]
     },
     "config": {
-        "platform": {
-            "php": "7.2.9"
-        },
         "sort-packages": true
     },
     "require": {
-        "infection/abstract-testframework-adapter": "^0.2.3",
+        "php": "^7.3",
+        "infection/abstract-testframework-adapter": "^0.3.0",
         "infection/include-interceptor": "^0.2.0",
         "symfony/filesystem": "^3.4.29 || ^4.0 || ^5.0",
         "symfony/process": "^3.4.29 || ^4.0 || ^5.0",