add impersonation.rb request
main impersonation functionality
* add IndexedPageItemView support as per http://msdn.microsoft.com/en-us/library/exchange/aa563549 for FindItem requests
* amend parsing of built response for extended_properties in lieu of rebuilding the response parser itself
Merge pull request #85 from TobiG77/features

Allow Pagination of FindItem calls via IndexedPageItemView