simple launch browser

launch_browser

#!/usr/bin/env python

from marionette import Marionette
from gaiatest.apps.browser.app import Browser

# remember to 'adb forward tcp:2828 tcp:2828'
m = Marionette('localhost', 2828)
m.start_session()
browser = Browser(m)
browser.launch()
browser.go_to_url('http://www.mozilla.com')
print browser.url
browser.tap_go_button()

# other stuff here:
n = m.find_element('css selector', 'iframe[src*="firefoxos"]')
n.get_attribute('src')
u'https://firefoxos.persona.org/sign_in#NATIVE'
m.switch_to_frame(n)