Merge pull request #2783 from jlipps/master

allow pushStrings to work with 'app' as package, not just file
Adding additional checks in doctor/dev.js and updating contributing.md
Remove setting sessionOverride to false

Remove setting sessionOverride to false when cleaning up the session.
This parameter should left as it is.
Users may specify this value to true in the args when starting Appium server. However, once a session is cleared, this parameter would be as it was, instead of setting it to false.
Merge pull request #2782 from moizjv/fix-2752

Adding additional checks in doctor/dev.js and updating contributing.md
Merge pull request #2785 from fbai/patch-1

Remove setting sessionOverride to false
add test for sessionOverride