v.0.3.1

CHANGES:

• JSS._error_handler() now adds a status_code attribute to exceptions.

FIXES:

• JSSObject.save() was confusing. If you created a new object with JSSObject() that conflicted with an existing object on the JSS, the save would fail with a JSSPutError. Now we check for conflicts and instead return a - JSSPostError with a more helpful error message.
• I mistakenly listed the preference key as jss_password in the README. Now the code and README agree: jss_pass is the correct key.