Update editor config and composer deps from upstream.

.editorconfig

@@ -1,15 +1,17 @@
-# This file is for unifying the coding style for different editors and IDEs
-# editorconfig.org
-
-# PHP PSR-2 Coding Standards
-# http://www.php-fig.org/psr/psr-2/
+# Drupal editor configuration normalization
+# @see http://editorconfig.org/
 
+# This is the top-most .editorconfig file; do not search in parent directories.
 root = true
 
-[*.php]
+# All files.
+[*]
+end_of_line = LF
+indent_style = space
+indent_size = 2
 charset = utf-8
-end_of_line = lf
-insert_final_newline = true
 trim_trailing_whitespace = true
-indent_style = space
+insert_final_newline = true
+
+[{composer.json,composer.lock}]
 indent_size = 4

composer.json

@@ -4,10 +4,11 @@
     "type": "composer-plugin",
     "license": "GPL-2.0+",
     "require": {
-        "php": ">=5.4.5",
+        "php": ">=7.0",
         "composer-plugin-api": "^1.1",
+        "composer/semver": "^1.4",
         "drupal-composer/drupal-scaffold": "^2.2",
-        "symfony/filesystem": "~2.8|~3.0"
+        "symfony/filesystem": "~3.0"
     },
     "config": {
         "bin-dir": "bin/"