title: Add or Subtract From 64bit Integer in Javascript
body: <p>Is there a simple way (hoping for a small function, not a library) to add or subtract from a 64bit integer in JavaScript?</p>
  
  <p>Example 64bit int: 291270990346989568</p>
  
  <p>Background: I am working with the Twitter API which has 64bit tweet ID's. I'd like to add or subtract one from those IDs to manipulate what results I get back from Twitter.</p>