release version 0.2.0

version 0.2.0 implements the following
- updated xmlrpc to version 1.1.1
- Errors sent to callback are now ```Error``` instances (as thats the defacto node.js standard.) **This might break implementations that check for strings in the callback.**
- ```.addWithDupCheck()``` (alias ```.upsertCon()```) method for saving an api call on contact upsert procedures.