Setting content directly does not allow for use of DOM queries #304
Description
I have an issue when trying to set the content of a page using content=
Example (using Ferrum 0.12)
browser = Ferrum::Browser.new
page = @browser.create_page
# Works as expected
page.go_to 'https://google.com'
page.at_css("a") # => #<Ferrum::Node ... >
# Raises an exception and cannot find node
page.content = "<html><body><a href='#'>Test</a></body></html>"
page.at_css("a") # => Could not find node with given id (Ferrum::NodeNotFoundError)
# Yet the body has certainly updated - it's as though the DOM isn't refreshed
puts page.body # => "<html><head></head><body><a href=\"#\">Test</a></body></html>"