Merge pull request #52 from ProjectMirador/bump-version-0.4.0

Bump to version v0.4.0

package.json

 {
   "name": "mirador-annotations",
-  "version": "0.3.2",
+  "version": "0.4.0",
   "description": "mirador-annotations React component",
   "main": "lib/index.js",
   "module": "es/index.js",