- Linting: Lint hidden ncurc.js file

- Docs: Add 6.0.0.md migration file
- Docs: Update Contributing, Testing (renamed to Development), Linting and ReleaseInstructions
- Docs: Info on submodules
- npm: Add scripts for updating submodules
- npm: Add `license-badges`, `build-docs`, and `copy` scripts to `prepublishOnly` script
- npm: Bump to 6.0.0

.ncurc.js

@@ -1,6 +1,8 @@
+'use strict';
+
 module.exports = {
-  "reject": [
-    // Old copy with jspdf which needs updating: https://github.com/SVG-Edit/svgedit/issues/51
-    "underscore"
+  reject: [
+    // Todo: Old copy with jspdf which needs updating: https://github.com/SVG-Edit/svgedit/issues/51
+    'underscore'
   ]
 };