update appium-instruments
add real xpath support making use of getElementByIndexPath
this depends on https://github.com/appium/appium-uiauto/pull/11
also depends on https://github.com/michaelkourlas/node-js2xmlparser/pull/10
partially addresses issue 2155
add tests for new '-real xpath' temporary loc strat
and test for new real xml page source
add deprecation warnings for old page source and xpath methods
update uiauto submodule
use our own fork of node-js2xmlparser
use indexpath find retry even when trying to find a single element that becomes stale
Merge pull request #2204 from jlipps/real-xpath

Real XML-based XPath for iOS