Uiautomator2

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* update atx-agent version
* typo (318)
* fix connect\_usb error

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* fix 317, fix 316

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* merge change
* remove pure-python-adb dependency, use adbutils.py instead
* format \_\_init\_\_.py, update adbutils with ADB Protocol
* update changelog
* part of job

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* limit pure-python-adb version, to fix from adb.client import error
* support args

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* remove cmd:init from fire.Fire, fix forward error when muti device connect to one machine
* upgrade atx-agent
* ext\_xpath support
* remove 3.7
* fix travis test again
* fix travis
* sort imports
* split code to different files
* Update README.md
* Update README.md
* remove debug with dict: which will lead misunderstanding
* update atx-agent version
* appveyor
* exedir detection everywhere
* fix
* come at me
* need android components nowadays
* travis 2018 switches from android-21 to android-22
* fix pip install requirements
* fix travis lang
* add emulator and tests to travis and update README
* fix typo. (278)

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* fix connect\_usb init error, close 276
* fix typo
* add set\_fail\_prompt function
* add d.touch.(down|move|up) in readme
* fix atxagent version code