Added .editorconfig file

Mainly to catch trailing whitespace and set default indent levels.

.editorconfig

@@ -0,0 +1,27 @@
+# EditorConfig: http://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Defaults for all editor files
+[*]
+insert_final_newline = true
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = true
+
+# YAML is fussy about indenting and charset
+[*.yml]
+indent_style = space
+indent_size = 2
+continuation_indent_size = unset
+charset = utf-8
+
+# Markdown is fussy about indenting
+[*.md]
+indent_style = space
+indent_size = 4
+
+# Jinja2 template files
+[*.j2]
+end_of_line = lf