Reconnect after bootstrap disconnect

We don't know if the bootstrap has disconnected until a command is issued and
the uiautomator runtest command crashes. The crash is detected, uiautomator is
restarted, and the command that detected the crash is resent.
Relaunch on failure
Must resend on adb crash
Store lastCmd after return
Merge pull request #356 from bootstraponline/reconnect_2

Reconnect after bootstrap disconnect