Added .editorconfig for easier editing.

Editor Config allows local per-project configuration to be expressed in a single
file, which makes it easy for one to work across many repos with many projects,
each of which may have its own preferred indentation, spacing, EOL, encoding,
etc. styles.

This change just adds 4-space indent for Python; other rules can be added quite
easily. The file has a pointer to the project's homepage which explains how to
install editor-specific plugins to handle this config and how to extend this
config further.

.editorconfig

@@ -0,0 +1,7 @@
+# For more info on EditorConfig, see: http://EditorConfig.org
+
+root = true
+
+[*.py]
+indent_style = space
+indent_size = 4