added helper for add by part function.
added upload by parts and fixed bug with updateItem, where type will not update.
v1 of ReST API updateItem no longer supports updating 'type'.  It must be performed on the commit() function.  Added wait as boolean options and additionalParams as dictionary.  The wait param allows the user to make async calls synchronous by waiting for complete or failure.  additionalParams allows for the specification of item parameters in key/value pairs.  This is where you have to set the 'type' value.  updateItem no longer accepts that parameter.
Changed multipart post to use urllib2 from httplib
dropped httlib library
fixed updateItem()
Merge pull request #18 from achapkowski/master

Changed various url based calls, additem, addbyparts, all calls urllib2 based
Merge branch 'master' of https://github.com/Esri/ArcREST