Update modules where possible and remove unused modules from package.json

In progress.

- [x] Update Express from 3.5.x to 3.17.x with changes for breaking changes
- [x] Upgrade Moment from 2.4.x to 2.8.x with changes for breaking changes
- [x] Use npm version of paypal-express-checkout as changes in fork are there too now
- [x] Specify version for nconf
- [x] Upgrade other packages without breaking changes