Correct outdated local.py name in readme.

Change-Id: Ic110ca3585878c957b08c0e55c84b5781a6075b9
Correct name of the chrome browser file.

Change-Id: Ib26a44d9b1dd43f78af1512df3915cad205eeb98
Change default Chrome handling to go via the server, update readme.

This modifies the chrome browser example to allow either direct
control of the driver, which it turns out is slow, or access via the
server which is faster. Also update the readme to reflect this, and
tidy it up in the process now that we (almost) always need the server.

Change-Id: I9ab86a8aaf2cd9dbf6793f9ac287e0eaa34321a6