It's a relatively recent change, but npm package names are now required to be lowercase:

• https://docs.npmjs.com/getting-started/using-a-package.json#requirements
• npm 3 installs wrong dependency module when having uppercase name npm/npm#9671 (comment)

and the capitalisation of "Select2" in it's package.json caused us some issues recently:
npm/npm#10401

Would you consider updating the name property in the package.json to be lowercase "select2"