Update to Crosswalk embedding API v2.

Embedding API v2 is in Crosswalk-8.
See https://crosswalk-project.org/jira/browse/XWALK-2002 for details.
Upgrade to XWalk 8.36.175.0
Update README with better instructions for getting the Crosswalk library
Merge branch 'master' into plugin_with_arm_binary

Conflicts:
	plugin.xml