Build: Don't assume the browser environment; smoke test on Node w/ jsdom

Fixes gh-1950
```
   raw     gz Compared to master @ d6c97abb744bfe8c67ab9158aecdb5bb1c05e47b    
  +122    +29 dist/jquery.js                                                   
    -9    +35 dist/jquery.min.js                                               
```