title: Swift : add BigInteger framework
body: <p>I have to work with huge numbers in swift (to implement RSA algorithm), so I'm looking for an equivalent to the Java's BigInteger class. In an other topic, I found this one : <a href="https://github.com/kirsteins/BigInteger" rel="nofollow">https://github.com/kirsteins/BigInteger</a> 
  So I'm trying to add this to my project following these steps :
  - I download and add the BigInteger.xcodeproj to my project
  In "Build Phases" :
  - Add "BigInteger" at "Target Dependencies"
  - Add "BigInteger.framework from 'BigInteger' target in 'BigInteger' project" to "Link Binary With Libraries"
  - Add "BigInteger.framework" to the "Copy Files"</p>
  
  <p>When I build the project, it "Build failed", but I cannot understand why there is a problem. I found a video on youtube <a href="https://www.youtube.com/watch?v=NBmfGdbOrMs" rel="nofollow">https://www.youtube.com/watch?v=NBmfGdbOrMs</a> describing the steps, I follow exactly these steps but the problem is still here...</p>
  
  <p>Do you have the same problem ? Do you find a solution ?</p>