Added an .editorconfig file.

.editorconfig

@@ -0,0 +1,25 @@
+# Adapted from: http://editorconfig.org/
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+# 4 space indentation and default charset
+[*.{php,coffee,js,less,css,html}]
+charset = utf-8
+indent_style = space
+indent_size = 4
+
+# One-offs
+
+[{package.json}]
+indent_style = space
+indent_size = 2
+
+[{composer.json}]
+indent_style = space
+indent_size = 4