Commit .editorconfig file.

See http://editorconfig.org for more info about EditorConfig

[ci skip]

.editorconfig

@@ -0,0 +1,20 @@
+# http://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+end_of_line = lf
+insert_final_newline = true
+
+[*.php]
+trim_trailing_whitespace = true
+max_line_length = 120
+
+[*.{md,yml}]
+indent_size = 2
+
+[{phpunit.xml,phpunit.xml.dist,phpunit.xml.travisci}]
+indent_size = 2