Add clear_network_traffic command
Merge pull request #401 from vickvu/master

Add clear_network_traffic function
Show PhantomJS version on Travis-CI
Take out `Process.kill` logic into separate method
Fix #382, #404 JRuby pending test

We grab all the output from PhantomJS (like console.log) in another thread and
when PhantomJS exits first as in related test when we send
`driver.browser.command('exit')` we will try to restart it. In order to do it we
stop server and client. We see this error `IOError: Stream closed` for the
client. It happens because JRuby tries to close pipe with
https://github.com/jruby/jruby/blob/jruby-1_7/core/src/main/java/org/jruby/RubyIO.java#L2067
which raises an error here
https://github.com/jruby/jruby/blob/jruby-1_7/core/src/main/java/org/jruby/RubyIO.java#L4753
It happens not just because IO was closed but because it was blocked on `eof?`
or `readpartial` call. As you can see the error will be raised in related thread
(it's not actually main thread but the thread that listens to the output) that's
why if you put some debug code after `rescue IOError` it won't be shown and in
fact the main thread will continue working after the raise. For instance:

    def restart
      stop
      start
    end

it will invoke `start` even if we have seen `IOError` in `stop` method because
the error has been raised in another thread. In order to fix it we don't have to
give a chance to block IO. `IO.select` shows that there's something to be read
in pipe.
Add test for within_frame with frame index.

See #185.
Merge pull request #411 from jimjh/master

Add test for within_frame with frame index.
update cliver dependency to pull in upstream fixes
Specs are green
Cherry-pick mouse events at from michiels