Bumps xpring-js to 5.1.1

High Level Overview of Change

5.1.1 of xpring-js was just released. No substantive changes, but this keeps demos up to date.

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] Refactor (non-breaking change that only restructures code)
[ ] Tests (You added tests for code that already exists, or your new feature included in this PR)
[ ] Documentation Updates
[X] Release