3 discrete changs. Debug logging, Performance, Extensibility API and README

I hope this is a simpler structure. I squashed into 4 commits.

0be989c Add debug logging of connection errors and test each exception case.
2108192 Minor performance improvements. Prevent double response parse and use XML dedicated parser method.
0780592 Allow login to parse extensibility href and add extensibility api call to retrieve link features
1ac4391 Correct readme code example and debuging aids.